Write capture for fibre channel fabric snapshot service
View Patent ↗The snapshot capability moving into the SAN fabric and being provided as a snapshot service. A well-known address is utilized to receive snapshot commands. Each switch in the fabric connected to a host contains a front end or service interface to receive the snapshot command. Each switch of the fabric connected to a storage device used in the snapshot process contains a write interceptor module which cooperates with hardware in the switch to capture any write operations which would occur to the snapshot data area. The write interceptor then holds these particular write operations until the original blocks are transferred to a snapshot or separate area so that the original read data is maintained. Should a read operation occur to the snapshot device and the original data from requested location has been relocated, a snapshot server captures these commands and redirects the read operation to occur from the snapshot area. If, however, the read operation is directed to the original drive, the read is provided from the original data areas, even if the data had been replaced. The snapshot server determines the existence of particular snapshot devices, allocates their storage locations, provides this information to both the service interfaces and the write interceptors and handles read and write operations to the snapshot device.
1. A network device for use in a fabric, with a host, a service interface device, a snapshot server and two storage devices coupled to the fabric, the network device comprising:
a first port for connection to a storage device;
at least a second port for coupling to the service interface device, the snapshot server and the host; and
a module coupled to said first port and said at least a second port for receiving a snapshot creation command provided by the service interface device, said command directing creation of a snapshot of data stored on the connected storage device, and for enabling capturing of write operations from the host to said data stored on the connected storage device.
2. The network device of claim 1 , wherein said module is further for caching existence of data blocks created in the snapshot and for requesting creation of a data block in the snapshot if not previously created.
3. The network device of claim 2 , wherein said module further allows captured write operations to proceed if the write operation is to a data block that has been created in the snapshot.
4. The network device of claim 1 , wherein said module is further for receiving a snapshot deletion command provided by the service interface device and for transmitting a snapshot deletion completion indication to the service interface device.
5. A switch for use in a fabric, with a host, a service interface device, a snapshot server and two storage devices coupled to the fabric, the switch comprising:
a first port for connection to a storage device;
at least a second port for coupling to the service interface device, the snapshot server and the host; and
a module coupled to said first port and said at least a second port for receiving a snapshot creation command provided by the service interface device, said command directing creation of a snapshot of data stored on the connected storage device, and for enabling capturing of write operations from the host to said data stored on the connected storage device.
6. The switch of claim 5 , wherein said module is further for caching existence of data blocks created in the snapshot and for requesting creation of a data block in the snapshot if not previously created.
7. The switch of claim 6 , wherein said module further allows captured write operations to proceed if the write operation is to a data block that has been created in the snapshot.
8. The switch of claim 5 , wherein said module is further for receiving a snapshot deletion command provided by the service interface device and for transmitting a snapshot deletion completion indication to the service interface device.
9. A method for operating a switch used in a fabric, with a host, a service interface device, a snapshot server and two storage devices coupled to the fabric, one of the storage devices being connected to the switch, the method comprising:
receiving a snapshot creation command provided by the service interface device, said command directing creation of a snapshot of data stored on the connected storage device; and
enabling capturing of write operations from the host to said data stored on the connected storage device.
10. The method of claim 9 , further comprising:
caching existence of data blocks created in the snapshot; and
requesting creation of a data block in the snapshot if not previously created.
11. The method of claim 10 , further comprising:
allowing captured write operations to proceed if the write operation is to a data block that has been created in the snapshot.
12. The method of claim 9 , further comprising:
receiving a snapshot deletion command provided by the service interface device; and
transmitting a snapshot deletion completion indication to the service interface device.