JP2010079331A - Snapshot management system and snapshot management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a snapshot management system having a snapshot function with a restoring function to suppress operation stop time and operation restart time to the minimum without deteriorating writing performance, while being a snapshot management method using differential information with excellent disk use efficiency. <P>SOLUTION: In the snapshot management system, a host computer 101 and a storage system 103 for providing the snapshot function are connected via a network 102, so as to be freely communicable. The host computer 101 recognizes the storage system 103, based on a time axis, as a volume where an operation volume to be actually used in a database and a business system is independent from a plurality of snapshots generated in the past. A perfect volume is assigned to a first snapshot being one of the snapshots, and the perfect content of the whole volume is recorded in a perfect volume recording area 105. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a snapshot management system and a snapshot management method having a snapshot function of a volume provided by a storage system or a file server.

Storage systems and file servers provide a snapshot function that replicates a volume at an arbitrary timing and refers to it when necessary or restores the entire volume. This snapshot function is used for the purpose of database and business data backup and failure recovery.
As a snapshot management method, a method of holding a snapshot using difference information from an operating volume as in Patent Document 1 is common.
JP 2007-94472 A

  As in Patent Document 1, in the case of a method of managing snapshots using difference information from the operation volume, there is a problem that the writing performance to the volume is degraded. This is because before writing to the operation volume, it is necessary to read the pre-change data and then save it to the difference area.

  In addition, when it is desired to restore the entire operation volume to a snapshot state for failure recovery, the difference information is written back to the operation volume. During this write-back, the operation volume cannot be used, so the database and business operation must be stopped. There is a method to copy the contents of the snapshot by preparing another volume in order to minimize the operation stop time. However, since it is necessary to copy the entire volume, it takes a long time to resume the operation.

  In view of the above situation, the present invention is a snapshot management method that uses differential information with high disk usage efficiency, but has a restoration function that minimizes operation stop time and operation restart time without degradation of write performance. An object is to provide a snapshot management system and a snapshot management method having a snapshot function.

In order to solve the above problems, the present invention provides the following configurations.
The invention according to claim 1 is a snapshot management system in which a host computer and a storage system that provides a snapshot function are communicatively connected via a network,
The storage system includes a controller for controlling access to a volume;
A full volume recording area for storing full volume data;
A differential recording area for storing differential data for holding a snapshot,
From the host computer, the storage system is recognized based on the time axis as an independent volume of the operation volume actually used in the database or business system and a plurality of snapshots created in the past,
A complete volume is allocated to the first snapshot, which is one snapshot, and the complete contents of the entire volume are recorded in the complete volume recording area,
In the second or third snapshot immediately before or after the first snapshot, differential data from the complete volume is held as a differential volume,
In the snapshot before the second snapshot, differential data from the immediately following snapshot is held as a differential volume,
In the snapshot after the third snapshot, differential data from the immediately preceding snapshot is held as a differential volume,
The operational volume is configured to hold differential data from the immediately preceding snapshot as a differential volume, and a snapshot management system is provided.

  According to a second aspect of the present invention, in the snapshot management system according to the first aspect, when data is read from the operational volume, if there is no differential data in the operational volume in each pattern, the latest snap A snapshot management method is provided, wherein block data is searched from a differential volume of a shot, the data is read out when it is found, and if no block data is found in the differential volume, the data is read out from the complete volume. Is.

  The invention according to claim 3 provides the snapshot management method according to claim 1, wherein a difference block is added to the difference volume of the operation volume when a write process is performed. To do.

  According to a fourth aspect of the present invention, in the snapshot management system according to the first aspect, when adding a snapshot, a new snapshot is created as a copy of the operational volume, and an empty difference is created for the operational volume. The present invention provides a snapshot management method characterized by assigning a differential volume created in a state.

  In the snapshot management system according to claim 1, in the snapshot management system according to claim 1, when deleting a snapshot, the difference information of the differential volume of the snapshot to be deleted is changed to the differential volume of the adjacent snapshot or The present invention provides a snapshot management method characterized by writing to a complete volume and then deleting a snapshot to be deleted.

  The invention according to claim 6 is the snapshot management system according to claim 1, wherein when the complete volume of the snapshot is moved to the immediately following snapshot, the complete volume is intermediate between the original snapshot and the immediately following snapshot. , The full volume block located in the differential block of the immediately following snapshot differential volume is added to the original snapshot differential volume, and the differential block of the immediately following snapshot differential volume is made into a complete volume. The present invention provides a snapshot management method characterized by moving.

  In the invention according to claim 7, in the snapshot management system according to claim 1, when the operation volume is restored to the contents of the snapshot, the complete volume is moved to the snapshot to be restored in advance before the restoration. Another object of the present invention is to provide a snapshot management method characterized in that the difference information of other snapshots is discarded, the snapshot is erased, and the difference information of the operation volume is cleared.

  According to the snapshot management system of the present invention, although it is a snapshot management method that uses differential information with good disk usage efficiency, it is possible to minimize deterioration in write and read performance and to continue operation. However, it is possible to provide a snapshot function having a restoration function with less operation stop time and operation resumption time by moving the complete volume to a snapshot at an arbitrary point and performing restoration.

Hereinafter, embodiments of the present invention will be described with reference to the drawings showing examples.
FIG. 1 is a system configuration diagram showing an embodiment of a snapshot management system of the present invention. The snapshot management system of this embodiment includes a host computer 101 on which a database or a business system operates, a storage system 103 that provides a snapshot function, and a SAN (Storage Area Network) that connects the host computer 101 and the storage system 103. A network 102 is used.
The storage system 103 includes a controller 104 that controls access to a volume, a complete volume recording area 105 that stores data of a complete volume, and a differential recording area 106 that stores differential data for holding a snapshot. The

  FIG. 2 is a diagram showing a management state of snapshots. From the host computer 201, the operation volume 202 actually used in the database or business system and the snapshots A to D (203 to 206) created in the past are recognized as independent volumes based on the time axis. The complete volume 209 is assigned to the snapshot B (204), and the complete contents of the entire volume are recorded in the complete volume recording area 212. The snapshot A (203) is held as a difference from the complete volume 209 as a differential volume A (208). The operation volume 202 is held as a difference from the difference volume A (208) as a difference volume E (207). The snapshot C (205) is held as a difference from the complete volume 209 as a differential volume C (210). The snapshot D (206) is held as a difference from the difference volume C (210) as a difference volume D (211). These difference data are stored in the difference recording area 213.

  FIG. 3 is a diagram illustrating a method of reading data from the operation volume. In this figure, the operational volume 301 and the snapshot A (302) visible from the host side are configured as a differential volume, and the snapshot B (303) is configured as a complete volume. In the pattern 307, since no difference is recorded in the difference volume E and the difference volume A, the block (304) of the complete volume is read as data. In the pattern 308, since there is no difference in the difference volume E but the difference is recorded in the difference volume A, the difference block 305 of the volume A is read as data. In the pattern 309, since the difference is recorded in the difference volume E, the difference block 306 of the difference volume E is read as data. As described above, when data is read from the operation volume 301, block data is searched from the latest differential volume, and data is read when it is found. Compared to the case of simply reading data from a complete volume, there is an overhead due to the search for the difference, but the read block size itself does not change, so if appropriate difference management is performed, performance degradation is minimized.

  FIG. 4 is a diagram showing a method of writing data to the operation volume. In this figure, the operational volume 401 and snapshot A (402) visible from the host side are configured as a differential volume, and the snapshot B (403) is configured as a complete volume. The writing process is a process of adding a difference block to the difference volume E as in patterns 404 to 406. Compared to simply writing data to a complete volume, there is an overhead due to the difference management update, but the write block size itself does not change, so if appropriate difference management is performed, performance degradation is minimized.

  FIG. 5 is a diagram showing a snapshot addition method. A state 501 is a state before a snapshot is added. A state 502 is a state immediately after adding a snapshot. A snapshot E (503) is newly created as a copy of the operational volume, and a differential volume F (504) created in an empty differential state is assigned to the operational volume.

  FIG. 6 is a diagram showing a snapshot deletion method. A state 601 is a state before the snapshot A (602) is deleted. A state 603 is a state immediately after the snapshot A is deleted. The difference information of the difference volume A of the snapshot A to be deleted is written to the complete volume of the adjacent snapshot B (604). Note that if a differential volume is assigned to an adjacent snapshot, it is written to that differential volume.

  FIG. 7 is a diagram showing a method for moving the arrangement of complete volumes. The state 701 is a state before moving. When the complete volume of the snapshot B (702) is moved to the snapshot A (703), the status is 704 during the movement. During migration, with the complete volume positioned in the middle of snapshot A and snapshot B, the complete volume block at the position of differential block (705) of differential volume A is added to differential volume B (706), A process of moving the difference block (705) of the difference volume A to the complete volume is performed. Since the differential migration process is sequentially performed in units of blocks, the operation volume can be read and written even during the migration process. When the movement is completed, the state 707 is entered.

  FIG. 8 is a diagram showing a method for restoring the operation volume to the contents of the snapshot. Before restoring, move the complete volume to the snapshot you want to restore beforehand. A state 801 is prepared to restore the snapshot C (802). The state after restoration is 805. The restoration process is performed by discarding the difference information of the snapshot B (803) and the snapshot A (804), deleting the snapshot, and clearing the difference information of the operation volume (806). Since these operations can be realized simply by clearing the difference management area, they are completed in an instant.

1 is a system configuration diagram of a snapshot management system according to an embodiment of the present invention. FIG. It is explanatory drawing which shows the snapshot management state of the snapshot management system which concerns on one embodiment of this invention. It is explanatory drawing which shows the data read-out system from the operation volume by this invention. It is explanatory drawing which shows the data write-in method to the operation volume by this invention. It is explanatory drawing which shows the addition method of the snapshot by this invention. It is explanatory drawing which shows the deletion method of the snapshot by this invention. It is explanatory drawing which shows the system which moves arrangement | positioning of the complete volume by this invention. It is explanatory drawing which shows the system which restores | restores the operation volume by the content of a snapshot by this invention.

Explanation of symbols

101, 201 Host computer 102 Network 103 Storage system 104 Controller 105, 212, 304 Complete volume recording area 106, 213 Difference recording area 202, 301, 401 Operation volume 203-206, 302, 303, 402, 403, 503, 602 702, 703, 802 to 804 Snapshots 207 to 211 Differential volume 305, 306, 705 Differential block

Claims (7)

A snapshot management system in which a host computer and a storage system providing a snapshot function are communicatively connected via a network,
The storage system includes a controller for controlling access to a volume;
A full volume recording area for storing full volume data;
A differential recording area for storing differential data for holding a snapshot,
From the host computer, the storage system is recognized based on the time axis as an independent volume of the operation volume actually used in the database or business system and a plurality of snapshots created in the past,
A complete volume is allocated to the first snapshot, which is one snapshot, and the complete contents of the entire volume are recorded in the complete volume recording area,
In the second or third snapshot immediately before or after the first snapshot, differential data from the complete volume is held as a differential volume,
In the snapshot before the second snapshot, differential data from the immediately following snapshot is held as a differential volume,
In the snapshot after the third snapshot, differential data from the immediately preceding snapshot is held as a differential volume,
The snapshot management system, wherein the operational volume is configured to hold differential data from the immediately preceding snapshot as a differential volume.   2. In the snapshot management system according to claim 1, when data is read from the operation volume, if there is no difference data in the operation volume in each pattern, block data is extracted from the difference volume of the latest snapshot. A snapshot management method characterized in that data is read out when data is found and block data is not found in the differential volume, and data is read out from the complete volume.   The snapshot management system according to claim 1, wherein when a write process is performed, a difference block is added to the difference volume of the operation volume.   2. The snapshot management system according to claim 1, wherein when adding a snapshot, a new snapshot is created as a copy of the operational volume, and a differential volume created in an empty differential state is created for the operational volume. A snapshot management method characterized by allocating.   2. In the snapshot management system according to claim 1, when deleting a snapshot, the difference information of the difference volume of the snapshot to be deleted is written to the difference volume or complete volume of the adjacent snapshot, and then deleted. A snapshot management method characterized by deleting a target snapshot.   2. The snapshot management system according to claim 1, wherein when the complete volume of the snapshot is moved to the immediately following snapshot, the complete volume is positioned in the middle of the original snapshot and the immediately following snapshot. Snap characterized by adding the full volume block located in the differential block of the snapshot differential volume of the current snapshot to the differential volume of the original snapshot and moving the differential block of the snapshot differential volume immediately after to the full volume Shot management method.   2. In the snapshot management system according to claim 1, when restoring the operation volume to the contents of the snapshot, the complete volume is moved to the snapshot to be restored in advance before restoration, and the difference information of other snapshots Snapshot management method, wherein the snapshot is erased by deleting the snapshot and the difference information of the operation volume is cleared.

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