Methods and systems for implementing shared disk array management functions
Multiple Array Management Functions (AMFs) are connected to multiple redundancy groups over a storage area network (SAN), such as a fiber-channel based SAN. The multiple AMFs share management responsibility of the redundancy groups, each of which typically includes multiple resources spread over multiple disks. The AMFs provide concurrent access to the redundancy groups for associated host systems. When a host requests an AMF to perform an operation on a resource, the AMF synchronizes with the other AMFs sharing control of the redundancy group that includes the resource to be operated on, so as to obtain access to the resource. While performing the operation, the AMF send replication data and state information associated with the resource such that if the AMF fails, any of the other AMFs are able to complete the operation and maintain data reliability and coherency.
1. In a data storage network, a method of maintaining data coherency using two or more array management functions (AMFs) that are able to concurrently access a redundancy group, the redundancy group including a plurality of resources,
a first one of the AMFs being operative to receive a request, from a host, to perform a first operation on data stored on a first one of the resources, the method comprising:
receiving a message from the first AMF at a second AMF sharing access to the first resource so as to permit access to the first resource by the first AMF;
receiving replication and state data from the first AMF at the second AMF concurrently with the first AMF beginning to perform the first operation on the data; and
upon the first AMF failing to complete the first operation on the data, completing the first operation on the data by the second AMF using the replication and state data from the first AMF.
2. The method of claim 1 , wherein the first operation is a write operation, the method further comprising receiving from the first AMF the data to be written to the first resource.
3. The method of claim 2 , wherein the message is a write invalidate request, and wherein, responsive to the invalidate request, the second AMF invalidates corresponding data stored in its cache.
4. The method of claim 2 , further comprising receiving replication and state data from the first AMF concurrently with performing of the write operation by the first AMF.
5. The method of claim 1 , wherein the first operation is a read operation.
6. The method of claim 5 , further comprising performing a search of a cache of the second AMF for a copy of the data requested in the read request.
7. The method of claim 6 , further comprising sending the requested data from the second AMF to the first AMF.
8. The method of claim 5 , wherein the message identifies the data in the request, the method further comprising searching the cache of the second AMF for the identified data, and forwarding the identified data to the first AMF if found in the cache.
9. The method of claim 1 , further comprising determining whether the data identified in the request is shared by one or more other AMFs.
10. A data storage network, comprising:
two or more controllers communicably coupled to a redundancy group, each controller having one or more array management functions (AMFs), wherein two or more of said AMFs are able to concurrently access the redundancy group, the redundancy group including a plurality of resources,
a first AMF being operative to receive a request from a host to perform an operation on data stored on a first one of the resources, each controller further including:
means for receiving a message from the first AMF at a second AMF so as to permit access to the first resource by the first AMF;
means for receiving replication and state data from the first AMF at the second AMF concurrently with the first AMF beginning to perform the first operation on the data; and
means active upon the first AMF failing to complete the first operation on the data for completing the first operation on the data by the second AMF using the replication and state data from the first AMF.
11. The data storage network of claim 10 , wherein the first operation is a write operation, and further comprising means for receiving from the first AMF the data to be written to the first resource.
12. The data storage network of claim 11 , wherein the message is a write invalidate request, and wherein, responsive to the invalidate request, the second AMF invalidates corresponding data stored in its cache.
13. The data storage network of claim 11 , further comprising means for receiving replication and state data from the first AMF concurrently with performing of the write operation by the first AMF.
14. The data storage network of claim 10 , wherein the first operation is a read operation.
15. The data storage network of claim 14 , further comprising means for performing a search of a cache of the second AMF for a copy of the data requested in the read request.
16. The data storage network of claim 15 , further comprising means for sending the requested data from the second AMF to the first AMF.
17. The data storage network of claim 14 , wherein the message identifies the data in the request, and further comprising means for searching the cache of the second AMF for the identified data and forwarding the identified data to the first AMF if found in the cache.
18. The data storage network of claim 10 , further comprising means for determining whether the data identified in the request is shared by one or more other AMFs.