Storage device and method for controlling storage device

Patent metadata

Field	Value
Publication number	US-2016004642-A1
Application number	US-201314770567-A
Country	US
Kind code	A1
Filing date	Dec 12, 2013
Priority date	Dec 12, 2013
Publication date	Jan 7, 2016
Grant date	—

Abstract

The storage device of the present invention provides a decompression VOL having no corresponding relationship (mapping) with a final storage media to a superior device, and receives accesses from the superior device to the decompression VOL. Then, data written into the decompression VOL is compressed on-line in a cache memory, and the compressed data is mapped to a compression VOL which is a volume mapped to a final storage media. At the same time, by maintaining and managing a mapping information between an area in the decompression VOL where data has been written and a location in the compression VOL to which compressed data of the relevant data is mapped, when a read request is received from a superior device regarding the decompression VOL, the storage device converts a location information in the decompression VOL designated by the read request to a location information of the final storage media.

First claim

1 . A storage device connected to a host computer, and having a processor, a cache device and a plurality of final storage media,
the storage device comprising: a first volume capable of being accessed from the host computer; a second volume which is a volume mapped to the first volume, and storing the data written from the host computer to the first volume in a compressed state; wherein when the processor receives a write request to the first volume and a write target data regarding the write request from the host computer, the processor (1) sets the write target data in a compressed state in the cache device and stores the same in a storage area within the cache device; (2) determines a storage location in the second volume of the write target data in the compressed state; (3) allocates a storage area in the final storage media to be mapped to the storage location in the second volume of the write target data in the compressed state, in response to the storage location being determined; and (4) reads the write target data in the compressed state from the cache device, and stores the write target data being read in the compressed state to an area in the allocated final storage area.

2 . The storage device according to claim 1 , wherein
the write request includes an information of an address in the first volume to which the write target data is to be written; the storage device has an address mapping table managing a corresponding relationship between an address in the first volume and a storage location in the second volume of the write target data in the compressed state; wherein the processor records a corresponding relationship between the address included in the write request and a storage location in the second volume to the address mapping table, when a storage location of the write target data in the compressed state in the second volume is determined; refers to the mapping table when a read request designating an address in the first volume is received from the host computer, and specifies a storage location in the second volume corresponding to an address included in the read request; reads a data in compressed state from the final storage media based on the storage location in the second volume, and stores the data in the cache device; and acquires a data having decompressed the data in the compressed state from the cache device, and transmits the acquired data to the host computer.

3 . The storage device according to claim 1 , wherein
the processor stores information of the determined storage location each time a process is performed to determine a storage location in the second volume of the write target data in the compressed state; when determining a storage location in the second volume of the write target data in the compressed state, determines a subsequent address of an address specified by an information of the storage location being stored as a storage location of the write target data in the compressed state in the second volume.

4 . The storage device according to claim 1 , wherein
when an amount of the write target data in the compressed state stored in the cache device becomes equal to or greater than a given amount, the processor determines a storage location in the second volume of the write target data in the compressed state.

5 . The storage device according to claim 4 , wherein
a storage area to be mapped to the storage location in the second volume of the write target data in the compressed state is a storage area within a RAID group configured of a plurality of final storage media; and when an amount of write target data in the compressed state stored in the cache device becomes equal to or greater than an amount corresponding to one stripe group size of the RAID group, the processor determines a storage location in the second volume of the write target data in the compressed state.

6 . The storage device according to claim 1 , wherein
a capacity of the second volume is greater than a total capacity of the plurality of final storage media.

7 . The storage device according to claim 1 , wherein
the cache device provides a first logical storage space and a second logical storage space to the processor; when the processor issues to the cache device a data storage request for storing the write target data having designated an address in the first logical storage space to the cache device; the cache device sets the write target data in a compressed state and stores in a storage area in the cache device; after the processor issues a mapping instruction to map the address in the first logical storage space and the address in the second logical storage space to the cache device, and further issues a data read request for reading the write target data stored in the cache device designating an address in the second logical storage space mapped to an address in the first logical storage space to the cache device; the cache device reads the write target data in a compressed state.

8 . A method for controlling a storage device connected to a host computer, and having a processor, a cache device and a plurality of final storage media,
the storage device comprising: a first volume capable of being accessed from the host computer; a second volume which is a volume mapped to the first volume, and storing the data written from the host computer to the first volume in a compressed state; wherein when the processor receives a write request to the first volume and a write target data regarding the write request from the host computer, the processor (1) stores the write target data into a storage area in the cache device after changing the write target data in a compressed state in the cache device; (2) determines a storage location in the second volume of the write target data in the compressed state; (3) allocates a storage area in the final storage media to be mapped to the storage location in the second volume of the write target data in the compressed state, in response to the storage location being determined; and (4) reads the write target data in the compressed state from the cache device, and stores the write target data being read in the compressed state to an area in the allocated final storage area.

9 . The method for controlling a storage device according to claim 8 , wherein
the write request includes an information of an address in the first volume to which the write target data is to be written; the storage device has an address mapping table managing a corresponding relationship between an address in the first volume and a storage location in the second volume of the write target data in the compressed state; wherein the processor records a corresponding relationship between the address included in the write request and a storage location in the second volume to the address mapping table, when a storage location of the write target data in the compressed state in the second volume is determined; refers to the mapping table when a read request designating an address in the first volume is received from the host computer, and specifies a storage location in the second volume corresponding to an address included in the read request; reads a data in compressed state from the final storage media based on the storage location in the second volume, and stores the data in the cache device; and acquires a data having decompressed the data in the compressed state from the cache device, and transmits the acquired data to the host computer.

10 . The method for controlling a storage device according to claim 8 , wherein
the processor stores information of the determined storage location each time a process is performed to determine a storage l

Assignees

• Hitachi Ltd

Inventors

• Sugimoto Sadahiro
• Yamamoto Akira
• Hironaka Kazuei

Classifications

• G06F11/1096 Primary

  Parity calculation or recalculation after configuration or reconfiguration of the system · CPC title

• G06F12/0864 Primary

  using pseudo-associative means, e.g. set-associative or hashing · CPC title

• G06F2212/283

  Plural cache memories · CPC title

• G06F2212/401

  Compressed data · CPC title

• G06F2212/1044

  Space efficiency improvement · CPC title