| 摘要 |
A method and apparatus for ensuring the coherence of multiple copies of the same data at multiple geographic locations is presented. The system operating system, the system operator or some combination of both may determine the physical disks having the file or comprising the disk families containing data which requires protection. Using the MIRROR CREATE commands in a Unisys MCP operating system environment, a mirrored disk pack set is made for each relevant physical disk identified. The disk pack set is distributed amongst at least two geographic locations. For each member of each disk pack set, the STORESAFE+command associates a site identifier with the member corresponding to the member's geographic location. During application processing, disk writes for one member of a mirrored set are performed for each member of the set. The MCP operating system checks the results of each disk write to each of the members of the mirrored disk set. If the MCP operating system determines that a write was successful for at least one member of the mirrored set at each geographic location, then a "good" I/O result is returned to the application and application processing continues normally. By contrast, if the MCP operating system determines that for least one site identifier, no member of the set assigned the identifier experienced a successful disk write, then an IOERROR is returned, and application processing may optionally be halted. |
