WO2018078741A1 - Appareil de stockage - Google Patents

Appareil de stockage Download PDF

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Publication number
WO2018078741A1
WO2018078741A1 PCT/JP2016/081714 JP2016081714W WO2018078741A1 WO 2018078741 A1 WO2018078741 A1 WO 2018078741A1 JP 2016081714 W JP2016081714 W JP 2016081714W WO 2018078741 A1 WO2018078741 A1 WO 2018078741A1
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Prior art keywords
storage device
physical
storage
data
stripe
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PCT/JP2016/081714
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English (en)
Japanese (ja)
Inventor
豊 大島
黒川　勇
栄寿 葛城
敦 田代
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株式会社日立製作所
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Priority to PCT/JP2016/081714 priority Critical patent/WO2018078741A1/fr
Publication of WO2018078741A1 publication Critical patent/WO2018078741A1/fr

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F11/00—Error detection; Error correction; Monitoring
    • G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
    • G06F11/08—Error detection or correction by redundancy in data representation, e.g. by using checking codes
    • G06F11/10—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F12/00—Accessing, addressing or allocating within memory systems or architectures
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/06—Digital input from, or digital output to, record carriers, e.g. RAID, emulated record carriers or networked record carriers

Definitions

  • the present invention relates to a data recovery technique in a storage apparatus.
  • RAID Redundant Arrays of Inexpensive / Independent Disks
  • the RAID technology is a technology for calculating redundant data such as parity from write data received from a host device such as a host computer, and distributing and storing the write data and parity in different storage devices.
  • a storage apparatus employing RAID technology divides a storage area on a volume provided to a host computer or the like into data units of a predetermined size called stripes, and uses N stripes (N ⁇ 1) among these stripes. To generate M (M ⁇ 1) redundant data (parity). Note that the size of the M redundant data generated here is equal to the stripe. These redundant data are also called stripes or sometimes called parity stripes. A set of N stripes and M parity stripes generated from the N stripes is called a stripe line.
  • the storage device stores (N + M) stripes belonging to one stripe line in different storage devices.
  • N + M stripes belonging to one stripe line
  • the storage device stores (N + M) stripes belonging to one stripe line in different storage devices.
  • the data regenerated by the rebuild process is stored in a reserved storage area secured in advance.
  • an empty storage device that does not store any data or redundant data is secured as a spare storage area.
  • data or redundant data is stored in the storage device disclosed in Patent Document 1.
  • a method is disclosed in which a part of each storage device used for storage is reserved as an unused area (spare area), and the regenerated data is distributed and stored in the spare area of each storage device. ing. By doing so, the write destination of the regenerated data is distributed, so that it is possible to expect an effect that the load can be distributed even during the rebuild process.
  • the compression ratio varies depending on the data contents. Therefore, when the compression rate of the data stored in the storage device is worse than originally assumed, there may occur a case where data cannot be stored in the storage device. For example, when the rebuild process described above is performed, there may occur a situation in which the regenerated data cannot be stored in the spare area. In this case, the data may be lost.
  • a storage apparatus includes a storage controller that receives write data from a host computer, a predetermined amount of physical area, and compresses the data to the physical area.
  • the storage controller manages more than (N + M) storage devices as a parity group, generates M parity from N data written from the host computer, and generates the N data and Each of the M parities is stored in different storage devices in the parity group.
  • N + M storage devices
  • M parity is stored in different storage devices in the parity group.
  • a spare stripe that is an area for storing data restored during the rebuild process is provided. It has been.
  • the storage controller normally suppresses the use of the physical area necessary for storing the data written to the spare stripe. Then, when a failure occurs in the storage device, use of a physical area of an amount necessary for storing data to be written in the spare stripe is permitted.
  • the present invention can prevent data loss when a storage device fails.
  • FIG. 3 is a conceptual diagram showing an example of arrangement of each stripe in the storage apparatus according to the embodiment. It is a figure showing the relationship between a logical volume and a virtual parity group. It is the conceptual diagram which showed the relationship between a virtual parity group and a parity group. It is explanatory drawing of a spare area
  • program may be used as the subject, but precisely, the program is executed by a CPU (processor) to perform a predetermined process. However, to prevent the explanation from becoming redundant, the program may be described as the subject. Therefore, in the following description, the process described with the program as the subject actually means that the CPU executes the process. Further, part or all of the program may be realized by dedicated hardware.
  • Various programs may be installed in each apparatus by a program distribution server or a computer-readable storage medium.
  • the computer-readable storage medium is a non-transitory computer-readable medium such as a non-volatile storage medium such as an IC card, an SD card, or a DVD.
  • FIG. 1 shows a configuration of an information processing system (computer system) including a storage apparatus according to an embodiment of the present invention.
  • the information processing system includes a storage apparatus 1 and one or more hosts 2.
  • the storage device 1 is connected to the host 2 via a storage area network (SAN) 3.
  • the host 2 is a computer that executes an application program used by a user, and operates as a requester that issues an I / O request to the storage apparatus 1.
  • the host 2 is a general-purpose computer such as a main frame or a personal computer.
  • An application program or the like executed on the host 2 issues an I / O request such as a read command or a write command to a volume (logical volume) provided by the storage apparatus 1.
  • SAN 3 is a network composed of, for example, fiber channel cables and fiber channel switches.
  • the storage apparatus 1 includes a storage controller (hereinafter also abbreviated as “controller” or “DKC”) 10 and a disk unit 11 including a plurality of storage devices.
  • the storage controller 10 includes a CPU 12 that executes control such as I / O processing performed in the storage apparatus 1, a memory 13, a front-end interface (FE I / F) 14 that is a data transfer interface with the host 2, and a disk unit 11.
  • a back-end interface (BE I / F) 15 and a management I / F 16 which are data transfer interfaces are interconnected via an internal switch 17.
  • the number of each component, such as CPU12 and FE I / F14 is not limited to the number shown by FIG.
  • the disk unit 11 is equipped with a plurality of storage devices for storing write data from the host 2, and each storage device is connected to the storage controller 10 via the BE I / F 15.
  • the storage device is, for example, an SSD 21 that uses a nonvolatile semiconductor memory such as a flash memory as a storage medium, or an HDD 22 that uses a magnetic disk as a storage medium.
  • a case where all the storage devices mounted on the disk unit 11 are SSDs 21 will be described unless otherwise specified.
  • BE I / F 15 has at least an interface controller and a transfer circuit.
  • the interface controller is a component for converting a protocol (SAS in one example) used by the storage device into a communication protocol (PCI-Express as an example) used in the storage controller 10.
  • the transfer circuit is used when the storage controller 10 transfers data (read, write) to the storage device.
  • FE I / F 14 has at least an interface controller and a transfer circuit, similarly to BE I / F 15.
  • the interface controller of the FE I / F 14 is for converting the communication protocol (for example, fiber channel) used in the data transfer path between the host 2 and the storage controller 10 and the communication protocol used in the storage controller 10. belongs to.
  • the CPU 12 performs various controls of the storage device 1.
  • the memory 13 is used to store programs executed by the CPU 12 and various management information of the storage device 1 used by the CPU 12.
  • the memory 13 is also used for temporarily storing I / O target data for the storage device.
  • the storage area in the memory 13 used for temporarily storing the I / O target data for the storage device is referred to as “cache”.
  • the memory 13 is composed of a volatile storage medium such as DRAM or SRAM, but as another embodiment, the memory 14 may be composed of a non-volatile memory.
  • FIG. 2 is a diagram illustrating a configuration example of the SSD 21.
  • the SSD 21 includes an SSD controller 200 and a plurality of FM chips 206.
  • the SSD controller 200 includes a processor (CPU) 201, an upstream I / F 202, a downstream I / F 203, a memory 204, and a compression / decompression circuit 207, which are interconnected via an internal connection switch 205.
  • SSD is a storage device using a semiconductor memory, particularly a nonvolatile semiconductor memory, and means a device having the same form factor as an HDD.
  • SSD is used as a word meaning an entire storage device including a plurality of flash memories and a controller for controlling them, and the external shape and the like are limited to general HDD and SSD form factors. It is not something.
  • the nonvolatile semiconductor memory used for the SSD is a magnetoresistive memory such as MRAM (Magnetoretic Random Access Memory), a resistance variable memory ReRAM (Resistivity Random Access Memory), and a ferroelectric memory.
  • MRAM Magnetic Random Access Memory
  • ReRAM Resistivity Random Access Memory
  • ferroelectric memory ferroelectric memory
  • Various semiconductor memories such as a certain FeRAM (Ferroelectric random access memory) may be used.
  • the upstream I / F 202 is an interface controller for performing communication between the SSD 21 and the storage controller 10.
  • the upstream I / F 202 is connected to the BE I / F 15 of the storage controller 10 via a transmission line (SAS link or PCI link).
  • the downstream I / F 203 is an interface controller for performing communication between the SSD controller 200 and the FM chip 206.
  • the CPU 201 performs processing related to various commands coming from the storage controller 10.
  • the memory 204 stores a program for controlling the SSD 21, management information, and the like. A part of the memory 204 is also used as a buffer for temporarily storing write data transmitted from the storage controller 10 together with a write command and data read from the FM chip 206.
  • a volatile memory such as a DRAM is used. However, a nonvolatile memory may be used for the memory 202.
  • FM chip 206 is a non-volatile semiconductor memory chip such as a NAND flash memory. As is well known, reading / writing of data in the flash memory is performed for each area of a predetermined size (for example, 8 KB) called a page in a set of a plurality of cells. Data erasure is performed for each block which is a set of pages.
  • a predetermined size for example, 8 KB
  • the compression / decompression circuit 207 is hardware having a function of compressing data or decompressing the compressed data.
  • the SSD 21 can compress the write data from the storage controller 10 by the compression / decompression circuit 207 and store it in the FM chip 206.
  • the storage controller 10 performs data compression and data expansion transparently.
  • the SSD 21 may be configured such that data is compressed and decompressed by the CPU 201 executing a program that performs compression and decompression.
  • the storage apparatus 1 stores the write data from the host 2 in the storage device (SSD 21 or HDD 22), but does not directly provide the host 2 with the storage space provided by the storage device.
  • the storage apparatus 1 provides the host 2 with a storage space different from the storage space provided by the storage device. In this embodiment, the storage space provided to the host 2 is called a “logical volume”.
  • the storage device 1 manages the storage area on the logical volume by dividing it into partial areas of a predetermined size called “stripes”.
  • a predetermined operation such as exclusive OR is performed on a predetermined number (for example, N) of stripes to obtain the same size as the stripe.
  • M redundant data are created. Since the created redundant data is the same size as the stripe, it is called a “parity stripe”.
  • a stripe used for creating redundant data is sometimes called a “data stripe”.
  • a set of a parity stripe and a data stripe used to generate the parity stripe is referred to as a “stripe line”.
  • each stripe (data stripe and parity stripe) included in one stripe line is stored in a different storage device.
  • N and M are integers of 1 or more).
  • each data stripe and parity stripe included in one stripe line are distributedly stored in (N + M) storage devices.
  • N + M the number of data stripes included in one stripe line
  • RAID group the combination of the (N + M) storage devices.
  • FIG. 3 is a diagram conceptually showing the relationship between the stripe line and the storage area of each storage device.
  • the number of data stripes included in one stripe line is 3 and the number of parity stripes is 1 will be described.
  • elements 21-1 to 21-8 represent storage spaces (“logical address spaces” to be described later) provided to the storage controller 10 by the respective SSDs 21 (SSD 21-1 to SSD 21-8).
  • Each box in 21-1 to 21-8 represents a stripe (data stripe or the like).
  • a box described as “D” represents a data stripe
  • a box described as “P” means a parity stripe.
  • a box labeled “S” is a stripe used when a failure occurs in the SSD 21, and in the present embodiment, this is called a “spare stripe” or “spare area”. Details will be described later.
  • elements 320-1 and 320-2 each represent a stripe line.
  • each stripe belonging to the same stripe line exists at the same position (address) on the storage device.
  • each stripe belonging to the same stripe line is not necessarily stored. It does not have to exist at the same address on the device.
  • each stripe line exists in the same storage device.
  • each stripe line 320-1, 320-2 has more than (N + M) storages.
  • an example will be described in which each stripe line belonging to one logical device is distributed and arranged in eight storage devices, and a combination of these eight storage devices is called a “parity group”.
  • FIG. 4 is a diagram showing the relationship between logical volumes and virtual parity groups.
  • an element 300 represents a logical volume
  • each box (boxes such as D (0) and D (1)) in the logical volume 300 represents a stripe (data stripe).
  • the logical volume does not include a parity stripe.
  • the elements 350-0.350-1, 350-2, and 350-3 are storage devices that are virtually defined by the storage apparatus 1 for address conversion, and are hereinafter referred to as virtual storage devices. .
  • a combination of virtual storage devices 350-0, 350-1, 350-2, and 350-3 (element 340 in the figure) is called a virtual parity group.
  • the virtual parity group may be abbreviated as VPG.
  • the virtual parity group is similar to the RAID group in the traditional RAID technology, and each stripe belonging to the same stripe line 320 is located at the same address on the virtual storage device. For example, in FIG.
  • FIG. 5 is a conceptual diagram showing the relationship between virtual parity groups and parity groups.
  • Each stripe included in the stripe line on the virtual parity group is distributed and arranged in each storage device (SSD 21) in the parity group.
  • SSD 21 storage device
  • each stripe included in the stripe line 320-1 on the virtual parity group is arranged in the SSD 21-1, 21-2, 21-3, 21-4, and the stripe line 320-2
  • the stripes included in are arranged in SSDs 21-2, 21-3, 21-4, and 21-5.
  • the arrangement example of each stripe on the SSD 21 described above is an example, and other arrangements may be performed.
  • There is an advantage that the load of I / O processing is distributed by distributing stripes to more storage devices (SSDs 21) than the virtual storage devices included in the virtual parity group.
  • the storage apparatus 1 may hold the mapping information between the stripes on the virtual parity group (virtual storage device) and the stripes of the parity group (storage device) for each stripe.
  • the storage apparatus 1 may provide a relationship that can be expressed by some conversion formula (or function) between the address on the virtual storage device and the address of the storage device. Good.
  • a storage apparatus employing the traditional RAID technology has one or a plurality of spare storage devices in case a storage device in a RAID group fails, and this storage device is called a “spare drive”.
  • this storage device is called a “spare drive”.
  • no data is written to the spare drive.
  • the storage device fails and the data recorded in the failed storage device is restored (rebuilt) by the RAID technology, the restored data is stored in the spare drive.
  • the storage apparatus 1 is provided with an area for storing restored data in advance in each storage device in the parity group, as in the technique described in Patent Document 1.
  • This area is not used during normal times (when no failure has occurred in the storage device), but is used when a failure has occurred in any storage device.
  • this area is called a “spare area” or “spare stripe”.
  • the ratio of the spare stripe to the total stripe in the storage device that is, A value expressed by the number of spare stripes in the storage device ⁇ the total number of stripes in the storage device is referred to as “spare area ratio”.
  • FIG. 6 shows the same parity group configuration as FIG.
  • a box labeled “S” is a spare stripe.
  • SSD 21-1 in the figure fails, some spare stripes are used to store the restored data (the box labeled “S ⁇ D” in FIG. 6 is restored). Represents the spare stripe used to store the data (or parity) generated).
  • the load is concentrated on the spare drive.
  • the load is specified at the time of data recovery. It is possible to prevent concentration on the storage device. Details of processing at the time of data recovery will be described later.
  • the SSD 21 compresses the write data from the storage controller 10 by the compression / decompression circuit 207 and stores it in the FM chip 206.
  • data compression is performed transparently for the storage controller 10.
  • the SSD 21 provides a storage space of a predetermined size to the storage controller 10. In this embodiment, this storage space is called a “logical address space”. In FIG. 7, element 20 represents a logical address space.
  • the storage controller 10 writes data to the SSD 21, it issues a write command specifying the address in this logical address space and the size of the write target data.
  • the storage controller 10 transmits a write command (and 64 KB write data) for writing 64 KB data to the head (address 0) of the logical address space to the SSD 21.
  • the SSD 21 compresses the 64 KB data to result in 8 KB compressed data, and the 8 KB compressed data is stored in the FM chip 206.
  • the storage controller 10 reads this data, by issuing a read command designating the head of the logical address space (address 0) and the read data size (for example, 64 KB), the 64 KB data stored earlier. Can be read out.
  • the SSD 21 decompresses (restores) 8 KB of compressed data by the compression / decompression circuit 207 to obtain 64 KB of data before compression, and the SSD 21 returns the decompressed data to the storage controller 10. Because. Therefore, the storage controller 10 recognizes as if the data is stored in an uncompressed state in the logical address space (even if the data is actually compressed and stored).
  • the relationship (mapping) between the area in the logical address space and the storage area (called “physical area”) of the FM chip 206 may not be static.
  • the SSD 21 manages the mapping between each area on the logical address space and the physical area of the FM chip 206, and the mapping is dynamically changed.
  • the data (the compressed data) written in the area 401 on the logical address space represents a state where it is stored in the physical area 411 of the FM chip 206.
  • the SSD 21 manages information that the physical area 411 is mapped to the area 401.
  • the SSD 21 when the SSD 21 receives an update request for the area 401 from the storage controller 10, the SSD 21 generates compressed data of the data written together with the update request, and secures a new physical area in which the compressed data is to be stored. The compressed data is stored in the reserved physical area. Then, the SSD 21 changes the mapping so that the physical area secured this time is mapped to the area 411.
  • the size of the logical address space provided by the SSD 21 to the storage controller 10 is called “logical capacity”.
  • the total capacity of the storage areas of all the FM chips 206 of the SSD 21 is called “physical capacity”.
  • the logical capacity is set larger than the physical capacity. This is because the data written in the SSD 21 is compressed, so that it is expected that a larger amount of data than the physical capacity can be stored in the SSD 21. For example, when the logical capacity is set to 8 times the physical capacity and the physical capacity of the SSD 21 is 1 TB, the logical capacity is 8 TB (that is, the storage controller 10 recognizes that the SSD 21 has a storage capacity of 8 TB).
  • the data size after compression can vary depending on the content of the data.
  • the logical capacity is set to 8 times the physical capacity, if all the data written from the storage controller 10 to the SSD 21 is compressed to a size of 1/8 or less, all the data is stored in the FM chip 206. it can.
  • the data size after compression may not be less than 1/8 of the data size before compression. When such data is written to the SSD 21, there may be no physical area in which data (after compression) can be written.
  • the state where there is no physical area in which data can be written is referred to as “the physical area is depleted”.
  • the SSD 21 cannot store the write data received from the storage controller 10 in the physical area. Therefore, the SSD 21 according to the present embodiment has a predetermined amount of physical area into which data can be written (for example, 10% of all physical areas). %), The write request from the storage controller 10 is not accepted thereafter. Details will be described later.
  • the storage controller 10 provides a spare stripe in addition to the data stripe and the parity stripe on the storage space (logical address space) of the SSD 21 constituting the parity group.
  • the spare stripe is an area that is not used (write is not performed) unless any storage device (SSD 21) in the parity group fails.
  • FIG. 8 shows an example of the logical physical capacity management table 800.
  • the logical physical capacity management table 800 is a table for recording information on the capacity (logical capacity, physical capacity) of each storage device, and is stored in the memory 13.
  • Information about one storage device is stored in each row (record) of the logical physical capacity management table 800.
  • This record has columns of PG # (801), PDEV # (802), logical capacity (803), physical capacity (804), logical usage (805), physical usage (806), and status (807). .
  • PDEV # (802) is an identification number of the storage device.
  • PG # (801) is the identification number of the parity group to which the storage device belongs.
  • the identification number of the storage device is referred to as “PDEV number”.
  • the PDEV number may be written as “PDEV #”.
  • the identification number of the parity group is called “PG number” and may be written as “PG #”.
  • the logical capacity (803) represents the logical capacity of the storage device
  • the physical capacity (804) represents the physical capacity of the storage device.
  • the logical usage (805) and physical usage (806) represent the logical usage and physical usage of the storage device, respectively.
  • the definitions of the logical usage amount and the physical usage amount in the present embodiment are as follows.
  • the logical usage is the total size of the area accessed from the storage controller 10 (the area where writing has been performed) in the logical address space.
  • the physical usage is the total size of the physical area allocated to the area written from the storage controller 10. In FIG. 5, when the storage controller 10 writes only to the areas 401, 402, and 403 on the logical address space 20, and the size of each of the areas 401, 402, and 403 is 64 KB, the logical usage amount is 192 KB. It is.
  • the data after compression of the data written from the storage controller 10 in each of the areas 401, 402, and 403 (which is assumed to be compressed to 8 KB) is written in the areas 411, 412, and 413 in the FM chip.
  • the physical usage amount is 24 KB.
  • Status (807) represents the state of the storage device. When the status (807) is “1”, this indicates that the storage device has failed and cannot be accessed.
  • the storage controller 10 stores the information (logical capacity (803), A request for acquiring physical capacity (804), logical usage (805), and information stored in physical usage (806) (for example, periodically) is issued, and the obtained information is logical capacity (803). , Physical capacity (804), logical usage (805), and physical usage (806). Since the logical capacity and the physical capacity are not variable values, the storage controller 10 acquires the logical capacity and the physical capacity once at the start of use of the storage device, and thereafter periodically acquires the physical usage from the storage device. You may make it acquire.
  • FIG. 9 is a configuration example of the PG management table 900.
  • the PG management table 900 is a table for managing information about parity groups, and is stored in the memory 13. Information about one parity group is stored in each record of the PG management table 900. Hereinafter, the contents of each column in the record will be described.
  • the column PG # (801) is a column for storing the PG number
  • the drive type (902) stores information indicating the types of storage devices constituting the parity group.
  • the parity group is the HDD 22. It is composed of In principle, the types of storage devices used for one parity group are the same.
  • the capacity (903) represents the logical capacity of the storage devices constituting the parity group.
  • the storage devices used for one parity group are the same. However, storage devices having different logical capacities may be included in the parity group.
  • the logical capacity of the storage device having the smallest logical capacity among the storage devices in the parity group is stored in the capacity (903).
  • Compression (904) indicates whether the storage device in the parity group has a compression function.
  • “ON” is stored in the compression (904), it means that the storage device in the parity group has a compression function, and the data written in the parity group is compressed.
  • the copy pointer (905) is information used at the time of rebuilding, and stores the address (LBA) of the rebuilding area in the failed storage device area (logical address space area). If none of the storage devices in the parity group has failed and the rebuild process has not been performed, an invalid value (referred to as “NULL”) is stored in the copy pointer (905).
  • the invalid value (NULL) is a value that is not normally used for the address of the storage device, such as -1.
  • the storage apparatus 1 When the storage apparatus 1 according to the present embodiment performs the rebuild process, data recovery is performed in order from the first stripe of the failed storage device.
  • the initial value of the copy pointer (905) is recorded as 0 (LBA of the first stripe), and when rebuilding is completed for the stripe indicated by the copy pointer (905), the copy pointer (905) is set to the address of the next stripe. Will be updated. Therefore, it means that the data of the address less than the copy pointer (905) in the area in the failed storage device has already been restored and stored in the spare stripe of another storage device, and the copy pointer (905) This means that the data at the above address has not been restored yet. Details of how the copy pointer (905) is used will be described later.
  • FIG. 10 shows a configuration example of the depletion threshold management table 1000.
  • the depletion threshold management table 1000 is a table for managing the usage state of the physical area, and is stored in the memory 13.
  • the depletion threshold value management table 1000 manages the usage state of the storage devices constituting the parity group for each parity group.
  • the record of the depletion threshold management table 1000 has columns of PG # (1001), a depletion threshold (1002), a physical capacity usage rate (1003), and an I / O suppression flag (1004).
  • PG # (1001) is an identification number of a parity group to be managed by the record of the depletion threshold management table 1000.
  • the physical capacity usage rate is a value that can be calculated for each storage device. For example, when the physical usage amount of a certain SSD 21 is u and the physical capacity is p, the physical capacity usage rate of the SSD 21 is u ⁇ p (Note that, as shown in FIG. 10, the physical capacity usage rate (1003) is expressed as a percentage, so the physical capacity usage rate (1002) A value obtained by multiplying u ⁇ p by 100 is stored). Since the physical usage and the physical capacity of the storage device are stored in the physical usage (806) column and the physical capacity (804) column of the logical physical capacity management table 800, respectively, the storage controller 10 stores the logical physical capacity management table 800. The physical capacity usage rate of each storage device can be calculated by referring to.
  • the physical capacity usage rate of the parity group is stored and managed in the depletion threshold management table 1000 (its physical capacity usage rate (1003)).
  • the maximum physical capacity usage rate is defined as the parity group usage rate among the physical capacity usage rates of a plurality of storage devices constituting the parity group. Therefore, the storage controller 10 calculates the physical capacity usage rate of each storage device belonging to the parity group, and stores the maximum physical capacity usage rate in the physical capacity usage rate (1003) of the depletion threshold management table 1000.
  • the depletion threshold (1002) is an index value used by the storage controller 10 to determine whether or not data can be written to the parity group. Specifically, when the physical capacity usage rate (1003) of the parity group is equal to or greater than the value stored in the depletion threshold (1002), the storage controller 10 does not write data to the parity group. A value such as 90% is set as the depletion threshold (1002).
  • the depletion threshold (1002) is a value that does not vary during normal times (when no failure occurs in the storage device), and the initially set value is maintained.
  • a value slightly smaller than the value that should be originally set is set as the depletion threshold (1002) at the time of initial setting (when a parity group is defined).
  • the depletion threshold (1002) is returned to a value that should be originally set.
  • the value that should be originally set in the depletion threshold (1002) is called the “pre-correction depletion threshold”. Assuming that the pre-correction depletion threshold is Y% and the spare area ratio is X%, “Y% ⁇ X%” is set at the time of initialization as shown in FIG. At the time of rebuild processing, the original value is returned to Y%.
  • the logical physical capacity management table 800 and the depletion threshold management table 1000 are periodically updated by a configuration information management program that is periodically executed by the CPU 12 of the storage controller 10.
  • a configuration information management program that is periodically executed by the CPU 12 of the storage controller 10.
  • the logical usage (805) and physical usage (806) in the logical physical capacity management table 800 are updated.
  • the physical capacity usage rate (1003) in the depletion threshold management table 1000 is also updated.
  • FIG. 11 shows a configuration example of the spare conversion table 1100.
  • the spare conversion table 1100 is used to specify the position of the storage destination stripe (spare stripe) of the rebuilt data when the storage device fails.
  • the position information of the stripe in the failed storage device and the position information of the corresponding spare stripe are recorded.
  • PDEV # (1101) and address (1102) are stripe position information in the failed storage device. Specifically, PDEV # (1101) is the PDEV number of the failed storage device, and address (1102) is the address of the stripe in the failed storage device. Note that information used as an address is, for example, LBA (Logical Block Address).
  • spare PDEV # (1103) and the address (1104) are spare stripe position information.
  • spare PDEV # (1103) is the PDEV number of the storage device where the spare stripe exists
  • address (1104) is the address of the spare stripe.
  • the PDEV # (1101) of the first record is “0x0000”
  • the address (1102) is “0”
  • the spare PDEV # (1103) is “0x0004”
  • the address (1104) is “0x1000”. This is because the data stored in the stripe with the address 0 (first stripe) in the PDEV with the PDEV # of 0x0000 is the stripe (spare) with the address of 0x1000 in the PDEV with the PDEV # of 0x0004. Stored in a stripe).
  • each record in the spare conversion table 1100 is created when any storage device in the parity group fails.
  • each record in the spare conversion table 1100 may be created at a time before the storage device fails.
  • the storage controller 10 may create each record in the spare conversion table 1100 at the start of using the parity group.
  • a spare stripe (spare stripe specified by spare PDEV # (1103) and address (1104)) associated with the stripe of the failed storage device (stripe specified by PDEV # (1101) and address (1102)). Since the determination method is arbitrary and is not directly related to the present embodiment, description thereof is omitted here.
  • the storage device 1 also stores information other than the management information described above in the memory 13. For example, the information for managing the mapping between the logical volume and the virtual parity group described with reference to FIG. 4 and the information for managing the mapping between the virtual parity group and the parity group described with reference to FIG. . However, since these pieces of information are not directly related to the description of the present embodiment, the description is omitted.
  • the storage apparatus 1 stores several programs for performing various processes in the memory 13. Here, only an outline of the program related to the description of the present embodiment will be described.
  • an I / O program for processing an I / O command (read command or write command; hereinafter simply referred to as “command”) received from the host 2
  • a destage program for writing data to the storage device The exhaustion check program for checking whether the physical area is exhausted and the rebuild program for performing the rebuild process are stored.
  • the I / O processing is performed when an I / O command is received from the host 2 to the logical volume, and is executed by the I / O program.
  • the access range (area on the logical volume) specified by the I / O command from the host 2 is smaller than one stripe size, and there are a plurality of access ranges. An example of a case that does not cross the stripe will be described.
  • Step 1201 The I / O program converts the address of the logical volume specified by the I / O command into an address on the virtual storage device constituting the virtual parity group.
  • Step 1202 The I / O program converts the address on the virtual storage device obtained in Step 1201 into the PDEV number of the storage device (SSD 21) constituting the parity group and the address on this storage device.
  • this conversion process is sometimes referred to as “VP conversion”.
  • the address obtained here is an address on the logical address space provided by the SSD 21 to the storage controller 10.
  • Step 1203 The I / O program determines whether the I / O command received from the host 2 is a write command or a read command. If the command is a write command (step 1203: Y), then step 1204 is performed. If the command is a read command (step 1203: N), then step 1211 is performed.
  • Steps 1204 and 1205 In step 1204, the I / O program performs a depletion check process. Although details of this process will be described later, the I / O program calls the depletion check program to cause the depletion check program to perform the depletion check process. If it is detected as a result of step 1204 that the physical area has been exhausted (step 1205: Y), the CPU 12 next executes step 1208. If the physical area has not been exhausted (step 1205) 1205: N), then step 1206 is performed.
  • Step 1206 When a write command is issued from the host 2, data (write data) to be written to the logical volume is sent from the host 2 to the storage device 1 together with the write command.
  • the I / O program stores this write data in the cache. Note that when data is stored in the cache, the I / O program stores the data with write position information (specifically, PDEV number and LBA). The data stored in the cache is later written to the storage device (at an appropriate timing).
  • the process in which the storage controller 10 writes data to the storage device is called “destage”. The flow of destage processing will be described later.
  • Step 1207 The I / O program responds to the host 2 that the write process is completed, and ends the process.
  • Step 1208 This process is performed when it is determined that the physical area is exhausted.
  • the I / O program does not write the write data sent from the host 2 and ends the processing (responses that the data cannot be written to the host 2).
  • Step 1211 The I / O program refers to the status (807) in the logical physical capacity management table 800 to determine whether the access destination storage device obtained in Step 1202 is inaccessible (status (807) is “1”. ” When the access is impossible (step 1211: Y), step 1212 is performed next, and when the access is possible (step 1211: N), step 1214 is performed next.
  • Step 1212 The I / O program compares the address of the access target storage device obtained in Step 1202 with the copy pointer (905) of the parity group to which the access target storage device belongs. If the copy pointer (905) is larger than the address of the access target storage device (step 1212: Y), it means that the data stored at that address has been restored by the rebuild process. In this case, step 1214 (normal read processing) is performed next. Conversely, when the address of the access target storage device is not less than the copy pointer (905) (step 1212: N), step 1213 (collection read processing) is performed next.
  • Step 1213 Here, collection read processing is performed. Since the collection read process is a known process, only the outline will be described here.
  • the I / O program reads data from all stripes (data stripe and parity stripe) belonging to the same stripe line as the access target stripe, and restores the read target data using the read data.
  • Step 1214 The I / O program performs normal read processing. Unlike the collection read process, the normal read process refers to a process of reading data stored in the storage device as it is without performing data restoration.
  • the I / O program reads data from the access target storage device.
  • the access target storage device is out of order (if the determination in step 1211 is affirmative)
  • the data is recorded in the spare stripe. Therefore, the I / O program refers to the spare conversion table 1100 to identify the spare stripe where the restored data is stored, and reads the data from the identified spare stripe.
  • spare conversion table 1100 For example, an example in which the contents of the spare conversion table 1100 are shown in FIG. 11 and the PDEV # and the address obtained in step 1202 are 0x0000 and 0x0100 will be described.
  • PDEV # (1101) and address (1102) are rows of 0x0000 and 0x0100, respectively
  • spare PDEV # (1103) and address (1104) are 0x0005 and 0x1000, respectively. is there.
  • the I / O program reads data from the address 0x1000 of the storage device whose PDEV # is 0x0005.
  • Step 1215 The I / O program returns the data read in Step 1214 or the data restored in Step 1213 to the host 2 and ends the process.
  • the destage process is executed when the data stored in the cache is written to the storage device in step 1206 described above, or when the storage controller 10 writes the restored data to the spare stripe in the rebuild process (described later).
  • the This process is performed by a destage program.
  • Step 1701 The destage program selects data that has not yet been written to the storage device from the data on the cache, and obtains information on the write position assigned to the data.
  • the destaging program performs the depletion check process by calling the depletion check program. At this time, the destaging program passes the write position information to the depletion check program, and determines whether the physical area of the write destination storage device is depleted.
  • Step 1702 If it is determined in step 1701 that the physical area is exhausted, step 1704 is performed next. If the physical area is not exhausted, step 1703 is performed next.
  • Step 1703 The destage program issues a write command to the storage device that is the data write destination, writes the data, and ends the process.
  • Step 1704 The destage program ends the process without writing to the storage device.
  • the depletion check program starts processing by being called from the I / O program (or rebuild program).
  • the depletion check program is called, the PDEV number of the access target storage device and the address (LBA) of the access target stripe are received from the caller program (I / O program or the like).
  • Step 1303 The depletion check program determines whether the access target storage device has a compression function. Specifically, the depletion check program first refers to the logical physical capacity management table 800 to identify the parity group number of the parity group to which the access target storage device belongs, and then refers to the PG management table 900. It is determined whether the compression (904) of the parity group to which the access target storage device belongs is “ON”. When the access target storage device does not have a compression function (step 1303: N), step 1307 is performed next. When the access target storage device has a compression function (step 1303: Y), step 1305 is performed next.
  • Step 1305 The depletion check program refers to the depletion threshold management table 1000 to determine whether the physical capacity usage rate (1003) of the parity group to which the access target area belongs is greater than or equal to the depletion threshold (1002).
  • the depletion check program next executes step 1306.
  • step 1307 is executed next.
  • Step 1306 The depletion check program determines that physical area depletion has occurred in the parity group to be accessed, returns to the calling program that the physical area has been depleted, and ends the process.
  • Step 1307 The depletion check program returns to the calling program that the physical area has not been depleted and ends the processing.
  • the rebuild process is started when access from the storage controller 10 becomes impossible because one (or a plurality of) storage devices in the parity group have failed.
  • the failed storage device is referred to as “failed device”, and the parity group to which the failed device belongs is referred to as “failed PG”.
  • the rebuild process can be executed in parallel with the I / O process (FIG. 12). That is, the storage apparatus 1 can execute the rebuild process while receiving an I / O command from the host 2.
  • Step 1401 The rebuild program determines a spare stripe corresponding to each stripe of the failed device and records the information in the spare conversion table 1100.
  • Step 1402 If the failed device has a compression function (this can be determined by referring to the column for compression (904) of the failed PG), the rebuilding program sets the failure PG depletion threshold (1002) to the original value. Return to (pre-correction depletion threshold). For example, when the spare area ratio of the faulty PG is 9%, the rebuild program adds 9% to the depletion threshold (1002) to increase the depletion threshold (1002).
  • Step 1403 The rebuild program initializes the copy pointer (905) of the fault PG (substitutes 0).
  • the rebuild program specifies the position of the stripe belonging to the same stripe line as the repair target stripe (PDEV # of the storage device to which it belongs and the LBA where the stripe exists), and reads out those stripes.
  • the rebuild program obtains the virtual storage device in the virtual parity group to which the stripe to be repaired belongs and the address on the virtual storage device, and based on that, each rebuilding program belongs to the same stripe line in the virtual parity group.
  • the address of the stripe (PDEV # and LBA of each storage device) is obtained, but description of these processes will be omitted.
  • step 1405 the rebuild program restores the data using the read stripe, and writes the restored data in the spare stripe. Since the information of the spare stripe corresponding to the restoration target stripe is recorded in the spare conversion table 1100 generated in step 1401, the rebuild program identifies the spare stripe to which the restoration data is written based on this information, and writes the information. Do.
  • Step 1406 The rebuild program updates the copy pointer (905) of the fault PG. Specifically, the rebuild program adds the stripe size to the copy pointer (905) so that the address pointed to by the copy pointer (905) becomes the stripe next to the restoration target stripe.
  • the stripe next to the repair target stripe may be a spare stripe. In that case, the rebuild program adds the stripe size to the copy pointer (905) again. This is because the spare stripe is not normally used and there is no need to restore data.
  • Step 1410 The rebuild program determines whether the copy pointer (905) of the failed PG has exceeded the termination LBA of the failed device. If the copy pointer (905) of the failed PG has not yet exceeded the termination LBA of the failed device (step 1410: N), the rebuild program returns to step 1404 for processing. Conversely, when the copy pointer (905) exceeds the terminal LBA of the failed device (step 1410: Y), step 1411 is performed next.
  • Step 1411 The rebuild program has an invalid value (called “NULL”) for the copy pointer (905) of the faulty PG.
  • NULL is a value that is not normally used for the address of the storage device (for example, ⁇ 1). ) Is stored, and the process ends.
  • the depletion threshold is updated (step 1402).
  • the depletion threshold is kept lower than the original value (subtracted by the amount corresponding to the spare area ratio), so it is in a state where writing to some physical areas is practically impossible. . This is to prevent the physical area for storing the data written in the spare stripe during the rebuild process from being exhausted (to ensure the physical area for data to be written in the spare stripe). is there.
  • the depletion threshold value is increased by executing the above step 1402, so that the rebuild program can write data to the physical area secured before the rebuild process.
  • Example 2 Since the configuration of the storage apparatus according to the second embodiment is the same as the storage according to the first embodiment, the illustration of the configuration is omitted.
  • the contents performed in the rebuild process are slightly different from those described in the first embodiment.
  • the rebuild process performed in the storage apparatus according to the second embodiment will be described. Since many parts of this process are the same as those described in the first embodiment, the following description focuses on the differences.
  • step 1407 is performed after step 1406 (processing for updating the copy pointer).
  • step 1407 the rebuild program updates the depletion threshold (1002) of the depletion capacity management table 1000.
  • the depletion threshold is gradually changed according to the progress of the rebuild process.
  • Step 1601 The rebuild program determines whether the failed device has a compression function. This determination is the same as step 1303 described in the first embodiment. If the failed device does not have a compression function (step 1601: N), the process ends. On the other hand, if the failed device has a compression function (step 1601: Y), then step 1602 is performed.
  • Step 1602 The CPU 12 calculates a rebuild program progress rate.
  • an index value indicating the progress of rebuilding a failed drive is referred to as “copy progress rate”.
  • the depletion threshold is equal to the “pre-correction depletion threshold-spare area ratio”, and as the copy pointer increases (that is, the rebuild process is performed for many stripes). As it is done), the depletion threshold increases gradually. When the rebuild process is completed, the depletion threshold becomes equal to the pre-correction depletion threshold.
  • Step 1604 Finally, the rebuild program stores the depletion threshold obtained in Step 1603 in the depletion threshold management table 1000 (the depletion threshold (1002)), and ends the process.
  • step 1304 when it is determined in step 1303 that the access target storage device has the compression function, step 1304 is executed before step 1305.
  • step 1304 the depletion check program determines whether or not the access target area is a spare stripe. If the area is not a spare stripe (step 1304: N), next step 1305 is executed as in the processing described in the first embodiment.
  • step 1304 when the access target area is a spare stripe (step 1304: Y), the depletion check program next executes step 1307.
  • a spare stripe a call is made that the physical area is not exhausted regardless of whether the physical capacity usage rate (1003) of the parity group to which the access target area belongs is equal to or higher than the depletion threshold (1002).
  • the depletion check process in the second embodiment is the same as that described in the first embodiment except that step 1304 is added.
  • the depletion threshold gradually increases with the progress of the rebuild process, so that the normal write process (a process for storing write data from the host 2) that occurs during the rebuild process is performed. It is possible to prevent a situation in which the physical area is excessively consumed by data and the data restored by the rebuild process cannot be stored. Also, in the exhaustion check process, if the access target area is a spare stripe, the exhaustion check is not performed (data can be written to the storage device even if the physical capacity usage rate exceeds the exhaustion threshold), so it is restored by the rebuild process. The data can be reliably written to the storage device (spare stripe).
  • depletion check process (FIG. 18) described in the second embodiment may be performed in the storage apparatus according to the first embodiment.
  • the depletion threshold (1002) of the depletion threshold management table 1000).
  • the physical area for writing (the physical area for writing the data restored by the rebuild process) was secured.
  • the physical area for the spare stripe may be secured by other methods. In Example 3, two methods will be described.
  • the first method is a method in which some physical areas are used in advance (apparently). Specifically, at the time of initial setting, the configuration information management program adds a value corresponding to the spare area ratio in advance to the physical usage (806) of the logical physical capacity management table 800. At this time, the pre-correction depletion threshold is set as the depletion threshold (1002) (that is, it is not necessary to set (pre-correction depletion threshold-spare area ratio)).
  • the configuration information management program sets (P ⁇ S ⁇ ) to the physical usage (806) of the storage device at the initial setting. 100) is set.
  • the configuration information management program updates the physical usage (806) of the logical physical capacity management table 800 using the physical usage acquired from the storage device.
  • the physical usage (806) includes the physical usage acquired from the storage device + (P ⁇ S ⁇ 100). Should be set.
  • the configuration information management program updates the physical capacity usage rate (1003) of the depletion threshold management table 1000
  • the physical capacity usage rate is used because the physical capacity (804) and physical usage amount (806) of the logical physical capacity management table 800 are used.
  • (1003) a value larger than the actual physical capacity usage rate (a value obtained by adding the spare area ratio) is stored. As a result, the physical area corresponding to the spare area ratio is not used.
  • step 1402 the rebuild program subtracts (P ⁇ S ⁇ 100) from the physical usage (806) of the storage device instead of correcting the depletion threshold (1002). Return to physical usage. As a result, during the rebuild process, the physical area for (P ⁇ S ⁇ 100) (TB) that has not been used until now can be used.
  • the second method is to reduce the physical capacity in advance. Specifically, at the time of initial setting, the configuration information management program sets a value obtained by subtracting a value corresponding to the spare area ratio from the physical capacity of the original storage device in the physical capacity (804) of the logical physical capacity management table 800. As in the first method, the pre-correction depletion threshold may be set as the depletion threshold (1002).
  • the configuration information management program sets (PP) to the physical capacity (804) of the storage device at the initial setting.
  • ⁇ S ⁇ 100) is set.
  • the configuration information management program updates the physical capacity usage rate (1003) of the depletion threshold management table 1000
  • the physical capacity usage rate is used because the physical capacity (804) and physical usage amount (806) of the logical physical capacity management table 800 are used.
  • (1003) a value larger than the actual physical capacity usage rate (a value obtained by adding the spare area ratio) is stored. As a result, the physical area corresponding to the spare area ratio is not used.
  • the rebuild program When the rebuild process is started, the rebuild program returns the physical capacity (804) of the storage device to the original physical capacity instead of correcting the depletion threshold (1002) in step 1402. As a result, during the rebuild process, the physical area for (P ⁇ S ⁇ 100) (TB) that has not been used until now can be used.
  • the method of returning the physical usage (806) or the physical capacity (804) of the storage device to the original value at the start of rebuilding has been described.
  • the storage apparatus according to the third embodiment may gradually return the physical usage (806) or the physical capacity (804) of the storage device to the original value in accordance with the progress of the rebuild process.
  • the depletion check process described in the second embodiment (the process of FIG. 18, that is, a method that does not perform the depletion check when writing is performed on a spare stripe) may be performed. .
  • the embodiment of the present invention has been described above, but this is an example for explaining the present invention, and is not intended to limit the present invention to the embodiment described above.
  • the present invention can be implemented in various other forms.
  • the storage apparatus 1 described in the embodiment the example in which the storage device is an SSD (storage apparatus using a flash memory) has been described, but the type of storage medium used for the storage device is not limited to the flash memory.
  • Any storage device may be used as long as it has a compression function.
  • the external storage apparatus 4 illustrated in FIG. 1 has a compression function
  • the external storage apparatus 4 may be used as a storage device.
  • the storage area on the logical volume provided to the host and the storage area of the (virtual) parity group are statically mapped (virtual volume to which each storage area of the logical volume is mapped at the time of definition).
  • the storage area on the parity group is uniquely determined), but the relationship between the logical volume storage area and the parity group storage area (stripe line) is limited to a fixed (static) configuration is not.
  • a logical volume formed by using a well-known technique, Thin-Provisioning technology may be provided to the host.
  • the storage area of the parity group (or stripe line) is allocated to the storage area only when a write request is received from the host computer to the storage area on the logical volume.
  • each program in the embodiment may be realized by hardware using hard wired logic or the like.
  • each program in the embodiment may be stored in a storage medium such as a CD-ROM or DVD and provided.

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Abstract

Selon un aspect de l'invention, un appareil de stockage comprend : une unité de commande de stockage qui accepte des données d'écriture provenant d'un ordinateur hôte ; et une pluralité de dispositifs de stockage qui possèdent des quantités prédéterminées de zones physiques et qui compressent des données puis stockent les données compressées dans les zones physiques. L'unité de commande de stockage gère plus de (N + M) unités des dispositifs de stockage en tant que groupe de parité, et génère M parités à partir des N éléments de données écrits par l'ordinateur hôte, puis stocke les M parités de façon individuelle dans le différents dispositifs de stockage du groupe de parité. Entre-temps, dans les espaces de stockage logiques des dispositifs de stockage, des bandes de réserve sont prévues pour servir de zones de stockage des données récupérées lors du traitement de reconstruction. L'unité de commande de stockage est caractérisée par l'inhibition de l'écriture sur les bandes de réserve dans des situations normales, et par l'autorisation d'utiliser certaines quantités de zones physiques nécessaires pour stocker les données à écrire sur les bandes de réserve lorsqu'elles sont déclenchées par l'apparition d'une défaillance dans les dispositifs de stockage.
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JP2014137758A (ja) * 2013-01-17 2014-07-28 Toshiba Corp 記憶装置および記憶方法
WO2016006072A1 (fr) * 2014-07-09 2016-01-14 株式会社日立製作所 Ordinateur de gestion et système de stockage
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JP2014137758A (ja) * 2013-01-17 2014-07-28 Toshiba Corp 記憶装置および記憶方法
WO2016006072A1 (fr) * 2014-07-09 2016-01-14 株式会社日立製作所 Ordinateur de gestion et système de stockage
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