| 摘要 |
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.
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