STORAGE APPARATUS AND METHOD OF CONTROLLING THE SAME

• US 20150193342A1
• Filed: 09/25/2012
• Published: 07/09/2015
• Est. Priority Date: 09/25/2012
• Status: Abandoned Application

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohara, Mao, Yoshida, Saeko, Matsushita, Takaki
• Application Number:
  US13/640,136
• Publication Number:
  US 20150193342A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0802 Addressing of a memory level in which the access to the desired data or data block requires associative addressing means, e.g. caches
• CPC Class Codes: G06F 12/0873 Mapping of cache memory to specific storage devices or parts thereof
• CPC Class Codes: G06F 12/0895 of parts of caches, e.g. directory or tag array
• CPC Class Codes: G06F 2212/1016 Performance improvement
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 2212/604 Details relating to cache allocation

Abstract

Provided is a storage apparatus to provide a data storage area to an external apparatus. The storage apparatus includes a storage drive to provide a physical storage area for the data storage area; and a storage control unit to manage the data storage area as an un-compression storage area that is a logical storage area for storing data in the external apparatus in an uncompressed form and as a compression storage area that is a logical storage area for storing data in the external apparatus in a compressed form, and to control each of data write processing and data read processing on the storage drive according to a data input-output request from the external apparatus. The compression storage area and the un-compression storage area each include a set of unit physical storage areas formed by dividing the physical storage area. The storage control unit includes an un-compression cache area that is a temporary memory area for storing un-compressed data, a compression cache area that is a temporary memory area for storing compressed data, and a read cache area that is a temporary memory area for storing data read from the compression storage area. When reading data from the compression storage area in response to a data read request from the external apparatus, the storage control unit decompresses the read data and stores the decompressed data to the read cache area. In a case where the storage control unit receives a data read request from the external apparatus and where read target data of the data read request is stored in the compression storage area, the storage control unit judges whether or not the read target data is stored in the read cache area. When judging that the data is stored in the read cache area, the storage control unit transfers the data stored in the read cache area to the external apparatus. When judging that the data is not stored in the read cache area, the storage control unit reads the read target data from the compression storage area, decompresses the data, and then transfers the decompressed data to the external apparatus.

Claims

1. A storage apparatus configured to provide a data storage area to an external apparatus, comprising:

a storage drive configured to provide a physical storage area for the data storage area; and

a storage control unit configured to manage the data storage area as an un-compression storage area that is a logical storage area for storing data in the external apparatus in an uncompressed form and as a compression storage area that is a logical storage area for storing data in the external apparatus in a compressed form, and to control each of data write processing and data read processing on the storage drive according to a data input-output request from the external apparatus,

wherein

the compression storage area and the un-compression storage area each include a set of unit physical storage areas formed by dividing the physical storage area,

the storage control unit includes an un-compression cache area that is a temporary memory area for storing uncompressed data, a compression cache area that is a temporary memory area for storing compressed data, and a read cache area that is a temporary memory area for storing data read from the compression storage area,

when reading data from the compression storage area in response to a data read request from the external apparatus, the storage control unit decompresses the read data and stores the decompressed data to the read cache area,

in a case where the storage control unit receives a data read request from the external apparatus and where read target data of the data read request is stored in the compression storage area, the storage control unit judges whether or not the read target data is stored in the read cache area,

when judging that the data is stored in the read cache area, the storage control unit transfers the data stored in the read cache area to the external apparatus, and

when judging that the data is not stored in the read cache area, the storage control unit reads the read target data from the compression storage area, decompresses the data, and then transfers the decompressed data to the external apparatus.

2. The storage apparatus according to claim 1, wherein

the unit physical storage areas forming the compression storage area are each set to have a smaller storage capacity than the unit physical storage areas forming the un-compression storage area.

3. The storage apparatus according to claim 1, wherein

a unit size of data stored in the compression cache area is set to be smaller than a unit size of data stored in the un-compression cache area.

4. The storage apparatus according to claim 1, wherein

when judging that a predetermined condition is satisfied, the storage control unit performs processing in background of reading data stored in the un-compression storage area, compressing the data, and storing the compressed data into the compression storage area.

5. The storage apparatus according to claim 4, wherein

a part of the physical storage area is fixedly allocated to the uncompression storage area, and

in a case where the storage control unit receives the data write request from the external apparatus during execution of data movement from the un-compression storage area to the compression storage area, the storage control unit performs processing of:

judging whether or not the data write request is made for data stored in the compression storage area;

when judging that the data write request is made for the data stored in the compression storage area, updating the data stored in the compression storage area, and data stored in the un-compression storage area corresponding to the data stored in the compression storage area.

6. The storage apparatus according to claim 1, wherein

when reading data from the compression storage area, the storage control unit judges whether or not the read target data is compressed data, and skips decompression of the read target data when judging that the read target data is not compressed data.

7. A method of controlling a storage apparatus configured to provide a data storage area to an external apparatus, the storage apparatus including

a storage drive configured to provide a physical storage area for the data storage area;

and

a storage control unit configured to manage the data storage area as an un-compression storage area that is a logical storage area for storing data in the external apparatus in an un-compressed form and as a compression storage area that is a logical storage area for storing data in the external apparatus in a compressed form, and to control each of data write processing and data read processing on the storage drive according to a data input-output request from the external apparatus, the compression storage area and the un-compression storage area each including a set of unit physical storage areas formed by dividing the physical storage area, the storage control unit including an uncompression cache area that is a temporary memory area for storing uncompressed data, a compression cache area that is a temporary memory area for storing compressed data, and a read cache area that is a temporary memory area for storing data read from the compression storage area, the method comprising;

when reading data from the compression storage area in response to a data read request from the external apparatus, decompressing, by the storage control unit, the read data and store the decompressed data to the read cache area;

in a case where the storage control unit receives a data read request from the external apparatus and where read target data of the data read request is stored in the compression storage area, judging, by the storage control unit, whether or not the read target data is stored in the read cache area;

when judging that the data is stored in the read cache area, transferring, by the storage control unit, the data stored in the read cache area to the external apparatus; and

when judging that the data is not stored in the read cache area, by the storage control unit, reading the read target data from the compression storage area, decompressing the data, and then transferring the decompressed data to the external apparatus.

8. The method of controlling a storage apparatus according to claim 7, wherein

the unit physical storage areas forming the compression storage area are each set to have a smaller storage capacity than the unit physical storage areas forming the un-compression storage area.

9. The method of controlling a storage apparatus according to claim 7, wherein

a unit size of data stored in the compression cache area is set to be smaller than a unit size of data stored in the un-compression cache area.

10. The method of controlling a storage apparatus according to claim 7, wherein

When judging that a predetermined condition is satisfied, the storage control unit performs processing in background of reading data stored in the un-compression storage area, compressing the data, and storing the compressed data into the compression storage area.

11. The method of controlling a storage apparatus according to claim 10, wherein

a part of the physical storage area is fixedly allocated to the uncompression storage area,

in a case where the storage control unit receives the data write request from the external apparatus during execution of data movement from the un-compression storage area to the compression storage area, the storage control unit performs processing of:

judging whether or not the data write request is made for data stored in the compression storage area;

when judging that the data write request is made for data stored in the compression storage area, updating the data stored in the compression storage area and data stored in the un-compression storage area corresponding to the data stored in the compression storage area.

12. The method of controlling a storage apparatus according to claim 7, wherein

when reading data from the compression storage area, the storage control unit judges whether or not the read target data is compressed data, and skips decompression of the read target data when judging that the read target data is not compressed data.