Storage control apparatus and method for compressing data for disk storage

• US 20030084238A1
• Filed: 11/15/2002
• Published: 05/01/2003
• Est. Priority Date: 01/13/1995
• Status: Active Grant

• Current Assignee: Hiroyuki Shimoi, Masanaga Tokuyo, Naoaki Okayasu, Shigeru Yoshida, Yoshiyuki Okada
• Original Assignee: Hiroyuki Shimoi, Masanaga Tokuyo, Naoaki Okayasu, Shigeru Yoshida, Yoshiyuki Okada
• Inventors: Okada, Yoshiyuki, Yoshida, Shigeru, Shimoi, Hiroyuki, Tokuyo, Masanaga, Okayasu, Naoaki
• Granted Patent: US 6,745,282 B2
• Time in Patent Office: Days
• US Class Current: 711/113
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 2212/312 In storage controller
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/064 Management of blocks
• CPC Class Codes: G06F 3/0674 Disk device

Abstract

A disk control apparatus includes a host interface unit for inputting and outputting data from and to a host, a cache memory for temporarily storing the input data, a compression/decompression unit for compressing or restoring the input data and outputting the data, a buffer memory for temporarily storing the compressed data outputted from the compression/decompression unit, a disk access control unit for controlling an access to a disk and a disk data management unit for making a management as to which position of a disk storage device to write the data stored in the cache memory.

Claims

1. A method of managing compressed data, comprising:

an allocating step of allocating a compressed segment representing data that is obtained by assembling plural pieces of data requested of writing and thereafter compressed the thus assembled data to a compression sector representing a buffer having a predetermined length;

a compression sector recording step of recording the compression sector allocated with the compressed segment in said allocating step on a disk storage device;

an invalid data area registering step of registering, when updating a content of the compressed segment in the compression sector recorded in said compression sector recording step, an area allocated with a pre-updating compressed segment as an invalid data area;

a comparing step of comparing a size of the invalid data area in the compression sector recorded in said compression sector recording step with a preset fiducial value;

a releasing process executing step of reading the compressed segment allocated to an area exclusive of the invalid data area from the compression sector including the invalid data area and executing a compression sector releasing process representing a process of changing the compression sector from which the compressed segment is read so that the compressed segments are allocable to a whole area thereof; and

a releasing process execution determining step of determining whether or not said compression sector releasing process executing step is performed on the basis of a result of the comparison in said comparing step.

2. A method of managing compressed data according to claim 1, further comprising:

a compression sector detecting step of detecting the compression sector including the largest invalid data area,

wherein the compression sector releasing process is executed with respect to the compression sector detected in said compression sector detecting step in said compression sector releasing process executing step.

3. A method of managing compressed data according to claim 2, wherein the compression section including the largest invalid data are is detected by making use of a table for storing a plurality of numerical values and the compression sectors having these numerical values in the form of sizes of the invalid data areas in a correspondence relationship in said compression sector detecting step.

4. A compressed data managing apparatus, comprising:

means for representing data that is obtained by assembling plural pieces of data requested of writing and, thereafter, compressing the thus assembled data to a compression sector representing a buffer having a predetermined length;

means for recording the compression sector allocated with the compressed segment on a disk storage device;

means for registering, when updating a content of the compressed segment in the compression sector, an area allocated with a pre-updating compressed segment as an invalid data area;

means for comparing a size of the invalid data area in the compression sector with a preset fiducial value;

means for reading the compressed segment allocated to an area exclusive of the invalid data area from the compression sector including the invalid data area and changing the compression sector from which the compressed segment is read so that the compressed segments are allocable to a whole area thereof; and

means for determining whether said means for reading changes the compressed sector in response to the result of comparison by said means for comparing.