Concurrent image backup for disk storage system

• US 5,487,160 A
• Filed: 12/04/1992
• Issued: 01/23/1996
• Est. Priority Date: 12/04/1992
• Status: Expired due to Term

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Symbios Logic Incorporated (Broadcom, Inc.), AT&T Global Information Solutions Company (NCR Voyix Corporation), Hyundai Electronics America Incorporated (SK Hynix Inc.)
• Inventors: Bemis, Edward D.
• Primary Examiner(s): Swann, Tod R.
• Assistant Examiner(s): Asta, Frank J.
• Application Number:
  US07/985,710
• Time in Patent Office: 1,145 Days
• Field of Search: 395/425, 395/441, 395/477, 395/489, 364/200 MS File, 364/900 MS File, 364/268, 364/285.1
• US Class Current: 711/114
• CPC Class Codes: G06F 11/1466 to make the backup process non-disruptive

Abstract

A disk drive within a disk array is utilized to capture the original image of data blocks that are updated, i.e., written over, through normal array processes during backup operations. The method captures original data images in a manner that allows the array to be restored to the state that existed at the initiation of the backup process. During execution of backup procedures data is moved in logical block sequence (0 to N) from the array to a backup device, such as a magnetic tape backup device, continuing until all array data has been transferred. Should a write request be received by the disk array controller during backup, the block address associated with the write request is checked to determine if the original data at that address has been written to the backup device. If the original data residing at the target block address has been written to the backup device the write request is scheduled for execution by the array controller. However, if the original data residing at the target block address has not yet been written to the backup device, the original images of the data blocks are copied to the spare drive prior to scheduled execution of the write request. Upon completion of the backup process, the original data images copied to the spare drive are also transferred to the backup device. Thus, all information necessary to restore the array to the state that existed at the time of initiation of the backup process is saved to the backup device. Although there are other sequences in which data could be moved to the backup device, the particular sequence described herein has the least impact (lowest overhead) on normal array activity during the backup process.

Claims

1. In a disk storage system, a method for concurrently backing up contents of said disk storage system to a backup storage device and processing a write I/O request received by said disk storage system, comprising the steps of:

sequentially copying data from said disk storage system to said backup storage device;

halting said process of sequentially copying data from said disk storage system to said backup storage device upon receipt of said write I/O request;

determining whether said write I/O request updates data residing in a storage area within said disk storage system which has not been copied to said backup device;

copying the data residing in said storage area to a temporary storage device if the data residing in said storage area has not been copied to said backup device;

executing said write I/O request to update the data residing in said storage area;

resuming said process of sequentially copying data from said disk storage system to said backup storage device; and

copying the contents of said temporary storage device to said backup storage device upon completion of said process of sequentially copying data from said disk storage system to said backup storage device.

2. The method according to claim 1, wherein said disk storage system is a disk array.

3. The method according to claim 2, wherein said temporary storage device is a spare drive within said disk array.

4. The method according to claim 3, wherein:

said disk array is a RAID level 3 disk array wherein data is multiplexed across a plurality of array drives;

said storage area comprises corresponding areas within each one of said plurality of array drives; and

said step of copying the data residing in said storage area to a temporary storage device includes the step of reading data from said corresponding areas and writing said data to said spare drive.

5. The method according to claim 3, wherein

said disk array is a RAID level 5 disk array employing a read-modify-write process for updating data and parity information stored upon first and second disk drives, respectively, in response to said write I/O request;

and

said step of copying the data residing in said storage area to a temporary storage device comprises the step of saving old data read from said first disk in accordance with said read-modify-write process to said spare drive.

6. In a disk array including a plurality of active disk drives and a spare disk drive, a method for backing up data from said array to a backup storage device, comprising the steps of:

sequentially copying data from said disk array to said backup storage device;

halting said process of sequentially copying data from said disk array to said backup storage device upon receipt of a write I/O request;

determining whether said write I/O request updates data residing in a storage area within said disk array which has not been copied to said backup device;

copying the data residing in said storage area to said spare drive if the data residing in said storage area has not been copied to said backup device;

executing said write I/O request to update the data residing in said storage area;

resuming said process of sequentially copying data from said disk array to said backup storage device; and

copying the contents of said spare drive to said backup storage device upon completion of said process of sequentially copying data from said disk storage system to said backup storage device.

7. In a disk storage system, a method for processing write I/O requests received by the disk storage system and backing up data from said disk storage system to a backup storage device, comprising the steps of:

executing said write I/O requests directed to areas within said disk storage system which have been backed up to said backup storage device; and

for write I/O requests directed to areas within said disk storage system which have not been backed up to said backup storage device, copying the data contents of said areas which have not been backed up to a temporary storage device and upon conclusion of backup procedures, transferring the data copied to said temporary storage device to said backup device.

8. A method for processing write I/O requests in a disk storage system, comprising the steps of:

receiving a write I/O request;

determining whether the write I/O request is directed to an area within said disk storage system which has been backed up to a backup storage device;

if the write I/O request is directed to said area within said disk storage system which has been backed up, executing the write I/O request; and

if the write I/O request is directed to an area within said disk storage system which has not been backed up, copying data contents of said area which has not been backed up to a temporary storage device.

9. A system for selectively executing a write I/O request in a disk storage system, comprising:

means for determining whether the write I/O request is directed to an area within said disk storage system which has been backed up to a backup storage device;

means for executing the write I/O request if the write I/O request is directed to said area within said disk storage system which has been backed up; and

means for copying data contents of an area which has not been backed up to a temporary storage device if the write I/O request is directed to said area which has not been backed up.