JP2001034535A - Cache memory backup system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To back up the data in a cache memory with a small electric power with a small circuit when the power supply is ceased in data processing. SOLUTION: At the time of write-caching data of one block as a processing unit, the data are written to a nonvolatile memory 5 while written to a cache memory 4. The cache memory 4 is equally divided into (m) blocks and the nonvolatile memory 5 is equally divided into (n) (m>n) blocks. A control circuit 2 invalidates the block of the data written to the nonvolatile memory 5 after the data are written back. If the power supply is ceased owing to a power failure, etc., the nonvolatile memory 5 is held as it is and when the power is supplied again, the data are written back to a magnetic disk drive 3 from the nonvolatile memory 5. The data can be held without requiring a battery for the backup process. Consequently, the data can be held by the small-capacity nonvolatile memory 5 without the need for a battery for the backup processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cache memory.
The present invention relates to a backup system, and more particularly to an improvement of a backup system when a power supply of a cache memory of a disk device or other electronic device is lost.

[0002]

2. Description of the Related Art In a data processing system, it is generally required to back up data even if the power is turned off during data processing and to prevent data loss. However, since the cache memory is composed of a volatile memory that loses the stored data when the power is turned off, a countermeasure is required. In order to respond to this request, for example, Japanese Unexamined Patent Application Publication No. 09-330277 discloses that, in the event of a power failure, processing such as writing back data from a cache memory to a disk device is efficiently performed,
There has been proposed a disk control device for saving power of a backup power supply at the time of a power failure.

As shown in FIG. 6, a disk control device disclosed in this publication has a disk control device 100,
A resource manager 13 that manages attributes of data stored in the cache memory 14 and saves data in the flash memory 15, monitors a remaining power amount of the battery unit 18, and writes data on the cache memory 14 at the time of a power failure. A voltage check circuit 16 for obtaining an amount of power to be saved required for executing the data saving process based on the number of attribute data, and a power supply from the battery unit 18 to the resource manager 13 and the flash memory 15 in response to an instruction from the voltage check circuit 16 And when the remaining power of the battery unit 18 becomes equal to or less than the saved power at the time of the power failure, the data saving process of only the data of the write data attribute is started.

[0004]

However, in the above-mentioned prior art, when the remaining power amount of the battery unit becomes equal to or less than the saved power amount, the backup power supply is used to perform the data saving process from the cache memory to the flash memory. There is a first problem of need. Also,
There is a second problem that the amount of circuits increases because the remaining amount of power for backup is calculated and data processing is performed accordingly.

As a conventional technique for solving such a problem, for example, a “memory system and data storage device” described in Japanese Patent Application Laid-Open No. H5-225074,
There is known a "backup control method in a file high-speed writing mechanism" described in JP-A-151094. In these techniques, when data is written to a cache, the same data is also written to a non-volatile memory, thereby reducing a backup power supply.

However, in such a technique, since the capacity of the nonvolatile memory is the same as the capacity of the cache memory, there is a problem that a large-capacity nonvolatile memory is required and it is extremely uneconomical.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cache memory capable of backing up data in a cache memory when power is cut off during data processing with low power.
To provide a backup system.

Another object of the present invention is to provide a cache memory backup system in which the capacity of a backup non-volatile memory is reduced.

[0009]

According to a first aspect of the present invention, there is provided a cache memory / backup system for controlling a data transfer with a host device, and a magnetic circuit for recording the data transferred to the control circuit. A disk memory, a cache memory for temporarily storing data transferred between the control circuit and the magnetic disk device, and a nonvolatile memory for writing data to the cache memory and writing the same data at the same time; Memory has the cache memory as a block of data processing unit.
N blocks (m>) having the same capacity as each of the equally divided blocks
n).

According to a second aspect of the present invention, there is provided a cache memory / backup system for controlling a data transfer with a host device, a magnetic disk device for recording the data transferred to the control circuit, A cache memory for temporarily storing data transferred between a circuit and the magnetic disk device, a volatile backup cache memory for writing the same data to the cache memory and writing the same data at the same time; A flash memory for holding data when the power is lost, a voltage detection circuit for detecting the power loss, and a notification of the power loss from the voltage detection circuit, the communication between the backup cache memory and the flash memory Performs data transfer and flashes when power is turned on. A backup control circuit that performs control to write back data of the memory to the magnetic disk device; and a backup power supply circuit that supplies power to the backup cache memory, the flash memory, and the backup control circuit when power is lost, The backup cache memory is characterized by comprising n blocks (m> n) having the same capacity as each block obtained by dividing the cache memory into m units of data processing units.

More specifically, the cache memory / backup system of the present invention is characterized in that when writing back from the cache memory to the magnetic disk device, the control circuit invalidates the block in the nonvolatile memory or the backup cache memory. And

In the cache memory / backup system of the present invention, writing to the cache memory is performed in units of blocks, a plurality of nonvolatile memories of the blocks are provided, and the cache memory is written to during the write cache. It is characterized in that the same data as the data is simultaneously written in the nonvolatile memory.

The data written in the nonvolatile memory is
When the write-back from the cache memory is completed, the cache memory is invalidated, and a new write cache is enabled. When the power is lost due to a power failure or the like, the non-volatile memory is retained as it is, and when the power is turned on again, the write-back is performed from the non-volatile memory for the block whose write-back has not been completed. Therefore, a battery for backup is not required, and data can be held only by a small-capacity nonvolatile memory.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the general operation of a cache memory will be described with reference to the block diagram of FIG.

In the cache write operation, when data from the host device (1) is received by the control circuit (2), the data is written to the cache memory (4) having a higher access speed than the magnetic disk device (3). The operation of writing this data to the cache memory (4) is called a write cache. The data written to the cache memory (4) is written to the magnetic disk device (3) by background processing when the write cache is not performed. The operation of writing data from the cache memory (4) to the magnetic disk device (3) is called write-back. If the cache hits during the cache read operation, the data in the cache memory (4) is read, transferred to the control circuit (2), and transferred to the host device (1). The cache memory (4) is used because the access speed is higher than that of the magnetic disk device (3). The above is the basic operation.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, there is shown a cache memory / backup system (hereinafter, referred to as a "backup system") as an embodiment of the present invention. The backup system includes a control circuit (2) for controlling data transfer with the host device (1), a magnetic disk device (3) for recording data transferred to the control circuit (2), and a control circuit (2). ) And the magnetic disk device (3), the cache memory (4) for temporarily storing data transferred thereto, and the cache memory (4) are divided into m blocks. n
(M> n).

Next, the operation of this embodiment will be described with reference to FIGS. FIG. 1 is a block diagram of the present embodiment, and FIG. 2 is a relationship diagram between the cache memory (4) and the nonvolatile memory (5) in FIG.

First, the storage areas of the cache memory (4) and the nonvolatile memory (5) are divided into units of blocks having the same capacity. As shown in FIG. 2, the cache memory (4) has m blocks, and the non-volatile memory (5) has n blocks.
It is divided into blocks and m> n. When the data of one block is write-cached from the control circuit (2) to the cache memory (4), the same data is simultaneously written to the nonvolatile memory (5). Then another one
When data of a block is write-cached from the control circuit (2) to the cache memory (4), the same data is also written to the non-volatile memory (5) in another block. A write-back process from the cache memory (4) to the magnetic disk device (3) is performed, and when the process is completed, the data of the corresponding block written in the nonvolatile memory (5) is invalidated, and a new data is written to the block. Enable write cache.

An example of this operation is shown in the nonvolatile memory (5) of FIG.
If the number of blocks is described as 2 blocks, the first 1
When the data of the block is write-cached to the block 2 of the cache memory (4), the same data is also written to the block 1 of the nonvolatile memory (5). Next, another one block of data is transferred to block 7 of the cache memory (4).
When write cache is performed, the same data is written to the block 2 of the nonvolatile memory (5). When the data in block 2 written in the cache memory (4) is written back to the magnetic disk device (3), the data in block 1 in the nonvolatile memory (5) is invalidated. Next, when writing another block of data to the block 5 of the cache memory (4), the same data is written to the block 1 of the nonvolatile memory (5) in which the above-mentioned data is invalidated.

When the power is lost due to a power failure or the like, the data written in the non-volatile memory (5) is kept as it is. Therefore, when the power is turned on again, if the data that has not been written back and is held in the nonvolatile memory (5) is written back from the nonvolatile memory (5) to the magnetic disk device (3), the data is lost. Can be prevented.

As another embodiment of the present invention, the basic configuration is as described above, but the nonvolatile memory (5) in the first embodiment shown in FIG. 1 is further devised. Will be described. FIG. 4 is a block diagram, and FIG. 5 is a diagram showing the relationship among the cache memory (4), the backup cache memory (6), and the flash memory (8) in FIG.

Referring to FIG. 4, in the present embodiment, a control circuit (2) for controlling data transfer with a higher-level device (1)
A magnetic disk device (3) for recording data transferred to the control circuit (2); and a cache memory (temporarily storing data transferred between the control circuit (2) and the magnetic disk device (3)). 4), a backup cache memory (6) that writes data to the cache memory (4) and simultaneously records the same data, and a flash memory (8) that retains the data in the backup cache memory (6) when the power is lost. A backup control circuit (7) for transferring data between the backup cache memory (6) and the flash memory (8) and performing control for writing back the data in the flash memory (8) to the magnetic disk device (3) when the power is turned on. ) And a voltage detection circuit (9) that detects power loss and notifies the backup control circuit (7). The source power supply and comprising a backup power supply for the flash memory and the backup cache memory (6) upon loss (8) and the backup control circuit (7) (1
0).

The operation of the backup system is as follows. If the nonvolatile memory (5) in FIG. 1 is replaced with a backup cache memory (6), the nonvolatile memory (5)
This is basically the same as the first embodiment using.
First, the storage areas of the cache memory (4) and the backup cache memory (6) are divided into blocks. As shown in FIG. 5, as in FIG. 2, the cache memory (4) is divided into m blocks, the backup cache memory (6) is divided into n blocks, and m> n.
And Then, the control circuit (2)
When the data is write-cached to the cache memory (4), the same data is simultaneously written to the backup cache memory (6).

Next, when data of another block is write-cached from the control circuit (2) to the cache memory (4), the same data is also written to another block in the backup cache memory (6). A write-back process is performed from the cache memory (4) to the magnetic disk device (3). When the process is completed, the data of the corresponding block written in the backup cache memory (6) is invalidated, and a new write cache is used. It becomes possible.

When the power supply is lost due to a power failure or the like, a voltage drop is detected by the voltage detection circuit (9) and the backup control circuit (7) is notified. The backup control circuit (7) writes the data in the backup cache memory (6) to the flash memory (8) by the notification, and
Retain data. The power at the time of transfer from the backup cache memory (6) to the flash memory (8) uses the backup power supply circuit (10).

Next, when the power is turned on again, the backup control circuit (7) writes the data held in the flash memory (8) back to the magnetic disk device (3) to restore the data state at the time of power failure. return.

As described above, in this embodiment, when the SRAM is used as the backup cache memory (6), the flash memory (8) is used only when the power supply is lost.
And the life of the flash memory (8) can be extended.

It should be noted that the present invention is not limited to the above embodiments, and each embodiment can be appropriately modified within the scope of the technical idea of the present invention.

[0030]

A first effect of the present invention is that a backup battery is not necessary or a low-power battery can be used even if it is necessary. This means that a large amount of power is not required, so that the space for the battery can be reduced.

A second effect is that the capacity of the backup nonvolatile memory can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a cache memory and a nonvolatile memory in FIG. 1;

FIG. 3 is a block diagram for explaining a basic operation of the cache memory;

FIG. 4 is a block diagram of a second embodiment of the present invention.

5 is a diagram showing the relationship between the cache memory, backup cache memory, and flash memory shown in FIG. 4;

FIG. 6 is a block diagram of a conventional technique.

[Explanation of symbols]

 Reference Signs List 1,20 Host device 2 Control circuit 3 Magnetic disk device 4,14 Cache memory 5 Non-volatile memory 6 Backup cache memory 7 Backup control circuit 8,15 Flash memory 9 Voltage detection circuit 10 Backup power supply 13 Resource manager 16 Voltage check circuit 17 switch circuit 18 battery unit 100 disk controller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G06F 12/16 310 G06F 12/16 340Q 340 13/00 301Y 13/00 301 1/00 341M 341N F term ( Reference) 5B005 JJ01 MM11 MM23 NN02 PP03 WW03 WW16 5B011 EB07 GG03 HH04 JA04 JB03 MB11 5B018 GA04 KA03 LA05 LA06 MA03 QA05 QA15 5B065 BA01 CC08 CE12 EA23 ZA14 5B083 AA09 BB03 CD01 GG01 DD01

Claims (4)

[Claims] 1. A control circuit for controlling data transfer between a host device, a magnetic disk device for recording data transferred to the control circuit, and a transfer between the control circuit and the magnetic disk device And a non-volatile memory in which the same data is written at the same time as write cache to the cache memory, wherein the non-volatile memory divides the cache memory into blocks each of which is a data processing unit. A cache memory / backup system comprising n blocks (m> n) having the same capacity as each block. 2. When data written simultaneously to the cache memory and the nonvolatile memory is written back from the cache memory to the magnetic disk device,
2. The cache memory backup system according to claim 1, wherein said control circuit invalidates said block of said nonvolatile memory. 3. A control circuit for controlling data transfer with a higher-level device, a magnetic disk device for recording data transferred to the control circuit, and a transfer between the control circuit and the magnetic disk device Memory for temporarily storing data to be read, a volatile backup cache memory for writing the same data to the cache memory at the same time as the write cache, and a flash memory for holding the data of the backup cache memory when power is lost A voltage detection circuit for detecting power loss; receiving a notification of power loss from the voltage detection circuit; performing data transfer between the backup cache memory and the flash memory; Write back data in the memory to the magnetic disk drive A backup control circuit that controls the backup memory, and a backup power supply circuit that supplies power to the backup cache memory, the flash memory, and the backup control circuit when power is lost. The backup cache memory performs data processing on the cache memory. A cache memory / backup system comprising n blocks (m> n) having the same capacity as each block divided into m equal units. 4. The data written simultaneously to the cache memory and the backup cache memory,
4. The cache memory / backup system according to claim 3, wherein when writing back from the cache memory to the magnetic disk device, the control circuit invalidates data in the backup cache memory.