Asynchronous data replication

• US 7,809,892 B1
• Filed: 04/03/2007
• Issued: 10/05/2010
• Est. Priority Date: 04/03/2006
• Status: Active Grant

• Current Assignee: AmZetta Technologies, LLC (American Megatrends International, LLC)
• Original Assignee: American Megatrends Incorporated
• Inventors: Chatterjee, Paresh, Muthirisavenugopal, Vijayarankan, Mahalingam, Anandh, Grandhi, Suresh
• Primary Examiner(s): Bataille; Pierre-Michel
• Application Number:
  US11/695,854
• Time in Patent Office: 1,281 Days
• Field of Search: 711/162, 711/161, 711/165, 711/112, 711/114, 714/6
• US Class Current: 711/143
• CPC Class Codes: G06F 11/2028 eliminating a faulty processor or activating a spare
• CPC Class Codes: G06F 11/2038 with a single idle spare processing component
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence

Abstract

Technologies are provided herein for asynchronous data replication. A primary server maintains and exposes a storage volume for use by storage clients. The primary server receives write operations directed toward the storage volume and performs the writes on the storage volume. The primary server also creates buckets containing each of the write operations. The buckets are opened at a first point in time and closed at a second point in time that may be selected based upon the contents of the buckets, a predefined time period, or based upon an indication from an application program. The buckets are transmitted to a second server computer asynchronously. When each bucket is received completely by the second server, its contents are written to a storage volume maintained by the second computer. The buckets may be created from pages of a write-back cache utilizing a zero buffer copy mechanism.

Claims

1. A computer system capable of asynchronously replicating data from a storage volume maintained at a first computer to a storage volume maintained at a second computer, the computer system comprising:

a first computer configured to receive one or more write operations directed to the storage volume maintained by the first computer, cache the one or more write operations in a write-back cache, segregate the one or more write operations in the write-back cache into a bucket utilizing a zero buffer copy mechanism, and transmit the bucket from the write-back cache to the second computer asynchronously, wherein one or more duplicate write operations are eliminated in the write-back cache prior to transmitting the bucket to the second computer; and

a second computer configured to receive the bucket at the second computer and apply the write operations in the bucket to the storage volume maintained by the second computer.

2. The computer system of claim 1, wherein the bucket comprises data in the write-back cache identifying write operations received at the first computer between a first point in time and a second point in time.

3. The computer system of claim 2, wherein the first computer is further configured to begin transmitting the bucket to the second computer prior to the second point in time.

4. The computer system of claim 3, wherein the second computer is further configured to apply the write operations in the bucket to the storage volume maintained by the second computer after the bucket has been completely received.

5. The computer system of claim 1, wherein transmitting the bucket from the write-back cache to the second computer comprises framing a plurality of small write operations into one large write operation.

6. A method for asynchronously replicating data from a first computer to a second computer, the method comprising:

receiving at the first computer one or more write operations directed to a storage volume maintained by the first computer;

caching the one or more write operations in a write-back cache of the first computer;

segregating the one or more write operations in the write-back cache into a bucket utilizing a zero buffer copy mechanism;

transmitting the bucket from the write-back cache to the second computer asynchronously;

receiving the bucket at the second computer; and

applying the write operations in the bucket to a storage volume maintained by the second computer, wherein one or more duplicate write operations are eliminated in the write-back cache prior to transmitting the bucket to the second computer.

7. The method of claim 6, wherein the bucket comprises pages of the write-back cache containing write operations received by the first computer between a first point in time and a second point in time.

8. The method of claim 7, wherein the first computer is configured to begin transmitting the bucket to the second computer prior to the second point in time.

9. The method of claim 8, wherein applying the write operations in the bucket to a storage volume maintained by the second computer comprises applying each write operation to the storage volume maintained by the second computer when the bucket has been completely received at the second computer.

10. The method of claim 9, wherein the second point in time is selected based on the number of write operations contained in the bucket.

11. The method of claim 9, wherein the second point in time is selected based on an amount of time that has passed since the first point in time.

12. The method of claim 9, wherein the second point in time is selected based upon data received from an application program.

13. The method of claim 6, wherein transmitting the bucket from the write-back cache to the second computer comprises framing a plurality of small write operations into one large write operation.

14. A computer-readable medium having computer-executable instructions stored thereon that, when executed by a primary computer, cause the primary computer to:

receive one or more write operations directed to a storage volume;

cache the one or more write operations in a write-back cache of the primary computer;

segregate the one or more write operations in the write-back cache into a bucket utilizing a zero buffer copy mechanism; and

transmit the bucket from the write-back cache to a remote server computer asynchronously, wherein one or more duplicate write operations es are eliminated in the write-back cache prior to transmitting the bucket to the remote server computer.

15. The computer-readable medium of claim 14, wherein the bucket comprises pages of the write-back cache containing write operations received by the primary computer between a first point in time and a second point in time.

16. The computer-readable medium of claim 15, wherein transmitting the bucket to a remote server computer asynchronously comprises beginning the transmission of the bucket to the remote server computer prior to the second point in time.

17. The computer-readable medium of claim 14, wherein the write operations are stored in the buckets in a manner that ensures write-order fidelity of the write operations.

18. The computer-readable medium of claim 14, wherein transmitting the bucket from the write-back cache to the remote server computer comprises framing a plurality of small write operations into one large write operation.