Raid-type storage system and technique

• US 6,442,659 B1
• Filed: 02/17/1998
• Issued: 08/27/2002
• Est. Priority Date: 02/17/1998
• Status: Expired due to Term

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Blumenau, Steven M.
• Primary Examiner(s): Kim, Matthew
• Assistant Examiner(s): PEUGH, BRIAN R
• Application Number:
  US09/024,177
• Time in Patent Office: 1,652 Days
• Field of Search: 711/114, 711/112, 711/111, 711/161, 711/162, 711/113, 455/6.1, 714/6
• US Class Current: 711/162
• CPC Class Codes: G06F 11/1076 Parity data used in redundant arrays of independent storages, e.g. in RAID systems
• CPC Class Codes: G06F 2211/1014 Compression, i.e. RAID systems with parity using compression techniques

Abstract

In an aspect, the invention features a method of storing data in a digital data storage system that includes a plurality of disk drives. The method involves receiving data at the data storage system; compressing the received data to generate a compressed version of the data; storing the received data on a first set of disk drives among the plurality of disk drives; and storing the compressed version of the received data on a parity disk drive so that the parity drive stores data that is redundant of data that is stored on the first set of drives.

Claims

1. A method of storing data in a digital data storage system that includes a plurality of disk drives, said method comprising:

receiving data at the data storage system;

compressing at least a portion of the received data to generate a compressed version of the received data;

performing a storing operation that initiates a first phase and a second phase, said first phase involving storing said at least a portion of the received data on a first set of disk drives among the plurality of disk drives, and said second phase involving storing the compressed version of the received data on a second disk drive among the plurality of disk drives so that the second disk drive stores data that is redundant of data that is stored on the first set of drives.

2. The method of claim 1 wherein the step of storing said at least a portion of the received data on the first set of drives involves storing said at least a portion of the received data without first compressing it.

3. The method of claim 2 further comprising assigning the second drive to be a dedicated drive for storing redundant information.

4. The method of claim 2 wherein the step of receiving data comprises storing said data in a cache memory and said method further comprises destaging said data from said cache memory to said plurality of drives, and wherein the step of destaging comprises performing said compressing step and said storing operation.

5. The method of claim 2 wherein the step of receiving data comprises storing said received data in a cache memory and said method further comprises destaging the stored received data from said cache memory to said plurality of drives, and wherein the step of destaging comprises said compressing step and said storing operation.

6. The method of claim 1 wherein the step of storing at least a portion of the received data on said first set of drives comprises first compressing said at least a portion of the received data and then storing it on said first set of drives.

7. A method of storing data in a digital data storage system that includes a plurality of disk drives, said method comprising:

receiving N blocks of data;

compressing the N blocks of data;

performing a storing operation that includes a first phase and a second phase, said first phase involving storing the N blocks of data in an uncompressed form on a first set of disk drives among the plurality of disk drives, wherein each block of the N blocks is stored on a different disk drive, and said second phase involving

storing the compressed data on a second disk drive among the plurality of disk drives so that the data storage system simultaneously stores the N data blocks in one physical location in uncompressed form and in another physical location in compressed form.

8. The method of claim 7 wherein the second drive is different from the first set of drives.

9. The method of claim 7 further comprising assigning the second drive to be a dedicated drive for storing redundant information.

10. The method of claim 7 wherein the step of receiving N blocks of data comprises storing said received N blocks of data in a cache memory and said method further comprises destaging the stored received data from said cache memory to said first set of drives, and wherein the step of destaging comprises the compressing step and said storing operation.

11. An apparatus for storing data comprising:

a plurality of disk drives;

a cache memory;

a compression engine; and

a controller which destages data stored from cache memory into the plurality of disk drives, wherein said controller is programmed to perform the functions of;

collecting a plurality of data blocks stored in the cache memory,

causing the compression engine to compress the data in the collected plurality of data blocks,

performing a storing operation that includes a first phase and a second phase, said first phase involving

storing the compress data on a first drive, said first drive being one of the plurality of disk drives, and said second phase involving

storing each of the plurality of data blocks in a different one of the plurality of disk drives none of which is the first drive.