Method, apparatus and program for migrating between striped storage and parity striped storage

• US 7,206,991 B2
• Filed: 10/15/2003
• Issued: 04/17/2007
• Est. Priority Date: 10/15/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Logic Corporation (Broadcom, Inc.)
• Inventors: Chatterjee, Paresh, Thangaraj, Senthil Murugan, Subramanian, Ramya, Kotte, Narasimhulu Dharanikumar, Hallyal, Basavaraj Gurupadappa
• Primary Examiner(s): Lamarre; Guy J.
• Application Number:
  US10/685,987
• Publication Number:
  US 20050086429A1
• Time in Patent Office: 1,280 Days
• Field of Search: 714 6- 7, 714/770, 711/114, 711/165
• US Class Current: 714/770
• CPC Class Codes: G06F 11/1096 Parity calculation or recalculation after configuration or reconfiguration of the system

Abstract

A mechanism is provided for migration between stripe storage and redundant parity striped storage. When a disk is added to a disk array, the mechanism migrates from RAID 0 to RAID 5. For each row, the mechanism calculates parity for the row and, if the parity position is not the new drive, the mechanism writes the data from the parity position to the new drive and writes the parity to the parity stripe position. If a drive fails, the mechanism migrates back from RAID 5 to RAID 0. For each row, if the parity position is not the failed drive, reads the data from remaining drives, XORs the data stripes to get failed drive data, and writes the failed drive data to the parity position. If a read or write is received for the failed drive, the mechanism simply redirects the read or write to the parity position.

Claims

1. A method for migrating from a non-mirrored, striped storage array that does not use parity to a parity striped storage array, the method comprising:

adding an additional new functioning drive to existing functioning drives of the non-mirrored, striped storage array to form the parity striped storage array;

for each row in the parity striped storage array, performing the following steps;

reading data from the existing drives;

calculating a parity stripe position for the row;

calculating a parity for the row;

determining whether the parity stripe position is in one of the existing drives;

responsive to determining that the parity stripe position is in one of the existing drives;

writing data from the one of the existing drives that includes the parity stripe position to the new drive; and

writing the parity to the one of the existing drives that includes the parity stripe position.

2. The method of claim 1, wherein the parity stripe position for the row is calculated using the following equation:

P_pos^R=(R,C),

where R is the row and C is the drive number corresponding to the parity stripe position, where C is defined as

C=(N−

((R)MOD(N))),

where N is a number of drives in the parity striped storage array.

3. The method of claim 2, further comprising:

responsive to a drive within the parity striped storage array failing to form a degraded parity striped storage array, restoring a modified non-mirrored striped storage array that does not use parity from the degraded parity striped storage array.

4. The method of claim 3, wherein restoring a modified non-mirrored striped storage array that does not use parity from the degraded parity striped storage array includes:

for each row in the parity striped storage array, performing the following steps;

calculating a parity stripe position for the row;

determining whether a drive of the parity striped storage array corresponding to the parity stripe position is the failed drive;

responsive to the drive corresponding to the parity stripe position not being the failed drive, reading data from the row, and determining failed drive data for the row; and

writing the failed drive data to the drive corresponding to the parity stripe position.

5. The method of claim 1, wherein the parity for the row is calculated using the following equation:

6. A method for restoring a modified non-mirrored striped storage array that does not use parity from a degraded parity striped storage array by removing a failed drive from the degraded parity striped storage array to form the modified, non-mirrored striped storage array, the method comprising:

for each row in the degraded parity striped storage array, performing the following steps;

calculating a parity stripe position for the row;

determining whether the parity stripe position is in the failed drive;

responsive to the parity stripe position not being in the failed drive, reading data from the row and using the data to determine failed drive data for the row;

writing the failed drive data to a drive that includes the parity stripe position; and

wherein the modified, non-mirrored striped storage array is formed after failed drive data is written into the parity stripe position for each row.

7. The method of claim 6, wherein the step of determining failed drive data for the row includes performing an exclusive OR operation on remaining stripes and a parity stripe to form failed drive data.

8. The method of claim 6, further comprising:

receiving an access request for a drive of the modified non-mirrored striped storage array;

determining whether a data position of the request corresponds to the failed drive;

responsive to the data position being the failed drive, determining a parity stripe position for the row and issuing the access request to a drive of the modified non-mirrored striped storage array corresponding to the parity stripe position.

9. The method of claim 6, further comprising migrating from the modified non-mirrored striped storage array to a parity striped storage array including adding an additional new functioning drive to existing functioning drives of the modified non-mirrored striped storage array to form the parity striped storage array.

10. The method of claim 9, further comprising:

for each row in the parity striped storage array, performing the following steps;

reading data from the existing drives;

calculating a parity stripe position for the row;

calculating a parity for the row;

determining whether the parity stripe position is in one of the existing drives;

responsive to determining that the parity stripe position is in one of the existing drives;

writing data from the one of the existing drives that includes the parity stripe;

position to the new drive; and

writing the parity to the one of the existing drives that includes the parity stripe position.

11. A data processing system, comprising:

a host;

a storage adapter; and

a non-mirrored striped storage array that does not use parity, wherein the host is connected to the non-mirrored striped storage array using the storage adapter,

wherein the host migrates to a parity striped storage array from the non-mirrored striped storage array by performing the following;

adding an additional new functioning drive to existing functioning drives of the non-mirrored, striped storage array to form the parity striped storage array;

for each row in the parity striped storage array, performing the following steps;

reading data from the existing drives;

calculating a parity stripe position for the row;

calculating a parity for the row;

determining whether the parity stripe position is in one of the existing drives;

responsive to determining that the parity stripe position is in one of the existing drives;

writing data from the one of the existing drives that includes the parity stripe position to the new drive; and

writing the parity to the one of the existing drives that includes the parity stripe position.

12. The data processing system of claim 11, wherein the parity stripe position for the row is calculated using the following equation:

P_pos^R=(R,C),

where R is the row and C is the drive number corresponding to the parity stripe position, where C is defined as

C=(N−

((R)MOD(N))),

where N is a number of drives in the parity striped storage array.

13. The data processing system of claim 11, wherein the parity for the row is calculated using the following equation:

14. The data processing system of claim 11, wherein the host restores a non-mirrored modified striped storage array that does not use parity from the degraded parity striped storage array responsive to a drive within the parity striped storage array failing to form a degraded parity striped storage array.

15. The data processing system of claim 14, wherein the host restores the modified non-mirrored striped storage array from the degraded parity striped storage array by performing the following:

for each row in the parity striped storage array, performing the following steps;

calculating a parity stripe position for the row;

determining whether a drive of the parity striped storage array corresponding to the parity stripe position is the failed drive;

responsive to the drive corresponding to the parity stripe position not being the failed drive, reading data from the row, and determining failed drive data for the row; and

writing the failed drive data to the drive corresponding to the parity stripe position.

16. A data processing system, comprising:

a host;

a storage adapter; and

a degraded parity striped storage array, wherein the host is connected to the striped storage array using the storage adapter,

wherein the host restores a modified non-mirrored striped storage array that does not use parity from the degraded parity striped storage array, by removing a failed drive from the degraded parity striped storage array to form the modified, non-mirrored striped storage array, by performing the following;

for each row in the degraded parity striped storage array, performing the following steps;

calculating a parity stripe position for the row;

determining whether the parity stripe position is in the failed drive;

response to the parity stripe position not being in the failed drive, reading data from the row and using the data to determine failed drive data for the row;

writing the failed drive data to a drive that includes the parity stripe position; and

wherein the modified, non-mirrored striped storage array is formed after failed drive data is written into the parity stripe position for each row.

17. The data processing system of claim 16, wherein determining failed drive data for the row includes performing an exclusive OR operation on remaining stripes and a parity stripe to form failed drive data.

18. The data processing system of claim 16, wherein the storage adapter receives an access request for a drive of the modified non-mirrored striped storage array, determines whether a data position of the request corresponds to the failed drive, and, responsive to the data position being the failed drive, determines a parity stripe position for the row and issues the access request to a drive of the modified non-mirrored striped storage array corresponding to the parity stripe position.

19. The data processing system of claim 16, wherein the host migrates from the modified non-mirrored striped storage array to a parity striped storage array including adding an additional new functioning drive to existing functioning drives of the modified non-mirrored striped storage array to form the parity striped storage array.

20. The data processing system of claim 19, further comprising:

for each row in the parity striped storage array, performing the following steps;

reading data from the existing drives;

calculating a parity stripe position for the row;

calculating a parity for the row;

determining whether the parity stripe position is in one of the existing drives;

responsive to determining that the parity stripe position is in one of the existing drives;

writing data from the one of the existing drives that includes the parity stripe position to the new drive; and

writing the parity to the one of the existing drives that includes the parity stripe position.

21. A computer readable medium having a computer program product for migrating from a non-mirrored striped storage array that does not use parity to a parity striped storage array, an additional new functioning drive being added to existing functioning drives of the non-mirrored striped storage array to form the parity striped storage array, the computer program product comprising:

instructions for performing the following steps for each row in the parity striped storage array;

reading data from the existing drives;

calculating a parity stripe position for the row;

calculating a parity for the row;

determining whether the parity stripe position is in one of the existing drives;

responsive to determining that the parity stripe position is in one of the existing drives;

writing data from the one of the existing drives that includes the parity stripe position to the new drive; and

writing the parity to the one of the existing drives that includes the parity stripe position.

22. A computer readable medium having a computer program product for restoring a modified non-mirrored striped storage array that does not use parity from a degraded parity striped storage array by removing a failed drive from the degraded parity striped storage array to form the modified, non-mirrored striped storage array, the computer program product comprising:

instructions for performing the following steps for each row in the degraded parity striped storage array;

calculating a parity stripe position for the row;

determining whether the parity stripe position is in the failed drive;

responsive to the parity stripe position not being in the failed drive, reading data from the row and using the data to determine failed drive data for the row;

writing the failed drive data to a drive that included the parity stripe position; and

wherein the modified, non-mirrored striped storage array is formed after failed drive data is written into the parity stripe position for each row.