Method and system for remote cache direct data placement

1. A machine implemented method, comprising;

receiving a read request at a first adapter to read data using a logical object managed by a second adapter;

the first adapter generating a command descriptor block for the second adapter to obtain the data and write the data at a location specified by the read request;

the second adapter retrieving the data from a storage location specified by the logical object and writing the data at the location specified by the read request;

the second adapter notifying the first adapter after writing the data; and

the first adapter notifying a client that send the read request.

2. The method of claim 1 , wherein the logical object is a logical unit number (LUN).

3. The method of claim 2 , wherein the LUN is based on storage space a local storage device managed by the second adapter.

4. The method of claim 2 , wherein the LUN is based on a storage space at a storage device accessible via a storage area network.

5. The method of claim 4 , wherein a storage controller at the second adapter obtains the data and writes the data at the location specified by the read request using a direct memory access (DMA) operation.

6. The method of claim 5 , wherein the storage controller is a Fibre Channel controller configured to interface with Fibre Channel storage devices.

7. The method of claim 1 , wherein the read request includes a scatter gather table identifying the storage location where the data is to be written.

8. A machine implemented method, comprising;

a first adapter generating a command descriptor block for a second adapter to obtain data in response to a read request from a client and write the data at a location specified by the read request;

the second adapter retrieving the data and writing the data at the location specified by the read request; and

the second adapter notifying the first adapter after writing the data.

9. The method of claim 8 , wherein the read request specifies a logical unit number (LUN) associated with a storage space where the data is stored.

10. The method of claim 9 , wherein the LUN is based on storage space at a local storage device managed by the second adapter.

11. The method of claim 9 , wherein the LUN is based on a storage space at a storage device accessible via a storage area network.

12. The method of claim 11 , wherein a storage controller at the second adapter obtains the data and writes the data at the location specified by the read request using a direct memory access (DMA) operation.

13. The method of claim 8 , wherein the read request includes a scatter gather table identifying the storage location where the data is to be written.

14. A system, comprising;

a first adapter receiving a read request from a client to read data using a logical object managed by a second adapter;

wherein the first adapter is configured to generate a vendor unique command descriptor block for the second adapter to obtain the data and write the data at a location specified by the read request; and

wherein the second adapter is configured to retrieve the data from a storage location specified by the logical object and writing the data at the location specified by the read request; and notify the first adapter after writing the data.

15. The system of claim 14 , wherein the logical object is a logical unit number (LUN).

16. The system of claim 15 , wherein the LUN is based on storage space a local storage device managed by the second adapter.

17. The system of claim 15 , wherein the LUN is based on a storage space at a storage device accessible via a storage area network.

18. The system of claim 17 , wherein a storage controller at the second adapter obtains the data and writes the data at the location specified by the read request using a direct memory access (DMA) operation.

19. The system of claim 17 , wherein the storage controller is a Fibre Channel controller configured to interface with Fibre Channel storage devices.

20. The system of claim 14 , wherein the read request includes a scatter gather table identifying the storage location where the data is to be written.