HP StorageWorks Storage Mirroring user's guide (T2558-96073, February 2008)

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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 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, file system changes from the user-defined data set
are tracked. Storage Mirroring 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.
Source
Target
User or application updates
part of a file
Only the changed portion
of the file is replicated
Up-to-date copy maintained
on the target