HP StorageWorks Storage Mirroring Recover User's Guide (T5437-96008, November 2009)

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Replication
Replication is the real-time transmission of file changes. Unlike other related
technologies, which are based on a disk driver or a specific application, the Storage
Mirroring Recover replication process operates at the file system level and is able to
track file changes independently from the file’s related application. In terms of network
resources and time, replicating changes is a more efficient method of maintaining a real-
time copy of data than copying an entire file that has changed.
After a source and target have been connected through Storage Mirroring Recover, file
system changes from the user-defined data set are tracked. Storage Mirroring Recover
immediately transmits these file changes to the target server. This real-time replication
keeps the data on the target up-to-date with the source and provides high availability
and disaster recovery with minimal data loss.
Unlike mirroring which is complete when all of the files have been transmitted to the
target, replication continuously captures the changes as they are written to the source.
Replication keeps the target up-to-date and synchronized with the source.
Failure monitoring and failover
Failover is the process in which a target stands in for a failed source. As a result, user
and application requests that are directed to the failed source are routed to the target.
Storage Mirroring Recover monitors the source status by tracking network requests and
responses exchanged between the source and target. When a monitored source misses
a user-defined number of requests, Storage Mirroring Recover assumes that the server
has failed. Storage Mirroring Recover then prompts the network administrator to initiate
failover, or, if configured, it occurs automatically.