System and method for data replication in a computer system

1. A computer system, comprising:

a source subsystem, wherein the source subsystem is operable to issue a write statement, wherein the source subsystem further comprises,

a source node operable to issue the write statement; and

a source storage device operable to store data and meta-data and changes thereto in response to the write statement;

a target subsystem, wherein the source node and the target node are communicatively coupled and wherein the target subsystem is external to the source subsystem;

a repository subsystem,

wherein the repository subsystem is external to each of the source subsystem and the target subsystem;

wherein the repository subsystem is communicatively coupled to each of the source subsystem and the target subsystem to facilitate the communication of data between the repository subsystem and the target subsystem and between the repository subsystem and the source subsystem; and

wherein the repository subsystem is operable to queue the write statement issued by and received from the source subsystem and deliver the write statement to the target subsystem; and

a network, wherein the source subsystem and target subsystem are communicatively coupled across the network.

2. The computer system of claim 1 , wherein the target subsystem further comprises:

a target node operable to receive the write statement; and

a target storage device operable to store data and meta-data and changes thereto in response to the write statement.

3. The computer system of claim 2 , wherein the data transfer mode is an asynchronous mode.

4. The computer system of claim 3 , wherein the repository subsystem further comprises:

a repository node operable to receive and transmit the write statement; and

a repository queue operable to queue the write statement.

5. The computer system of claim 4 ,

wherein the source node is operable to send the write statement to the repository node;

wherein the repository node is operable to queue the write statement in the repository queue; and

wherein the target node is able to receive the write statement from the repository subsystem.

6. The computer system of claim 4 ,

wherein the source node is operable to send the write signal to the repository node when the source subsystem is currently unable to replicate the write statement;

wherein the repository node is operable to queue the write statement in the repository queue; and

wherein the target subsystem is able to receive the write statement from the repository subsystem when the target subsystem is able to replicate the write statement.

7. The computer system of claim 6 , wherein the source node is operable to send the write statement to the repository subsystem if the source node receives a choke signal from the target subsystem.

8. The computer system of claim 6 , wherein the target node is operable to send the choke signal to the source node if the target subsystem is unable to replicate the write statement.

9. The computer system of claim 6 , wherein the target subsystem further comprises a target queue associated with a choke threshold and wherein the target subsystem is operable to queue the write statement if the target queue is not above the choke threshold.

10. The computer system of claim 9 , wherein the target node is operable to send the choke signal to the source node if the target node is unable to replicate the write statement and the target queue is above the choke threshold.

11. The computer system of claim 6 , wherein the repository queue is associated with a choke threshold and is operable to queue the write statement if the repository queue is not above the choke threshold.

12. The computer system of claim 11 , wherein the repository node is operable to send a choke signal to the source node if the repository queue is above the choke threshold.

13. The computer system of claim 12 , wherein the source subsystem further comprises a source queue.

14. The computer system of claim 13 , wherein the source node is operable to queue the write statement in the source queue if it receives a choke signal from the repository node.

15. The computer system of claim 4 , further comprising a plurality of repository subsystems.

16. The computer system of claim 15 , wherein the content of each repository queue is mirrored in at least one other repository queue.

17. A method of data replication in a computer system, comprising a source subsystem, a target subsystem, and a repository subsystem, wherein the repository subsystem is external to and communicatively coupled to each of the source subsystem and the target subsystem, and wherein the target subsystem is external to the source subsystem, comprising:

issuing a write statement at the source subsystem;

delivering the write statement to the repository subsystem for storage at the repository subsystem for later transmission to the target subsystem, wherein the repository subsystem queues the write statement for later transmission to the target subsystem; and

pulling the write statement from the repository queue when the target subsystem is able to handle the write statement;

replicating the write statement in the target subsystem.

18. The method of claim 17 , wherein the write statement is delivered to the repository subsystem if the target subsystem is unable to handle the write statement.

19. The method of claim 18 , wherein the target subsystem further comprises a target node operable to receive the write statement.

20. The method of claim 19 , wherein the target subsystem is unable to handle the write statement if the target node cannot handle the write statement.

21. The method of claim 19 , wherein the target subsystem further comprises a target queue associated with a choke threshold and operable to queue the write statement if the target queue is below the choke threshold.

22. The method of claim 21 , wherein the target subsystem is unable to handle the write statement if:

the target node is unable to handle the write statement; and

the target queue is unable to queue the write statement.