Intersite And Intrasite Replication Sets - HP P2000 Reference Manual
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Also See for P2000:
- Reference manual (448 pages) ,
- Deployment manual (74 pages) ,
- Release note (18 pages)
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Figure 4
Intersite and intrasite replication sets
Remote replication uses snapshot functionality to track the data to be replicated and to determine the
differences in data updated on the master volume, minimizing the amount of data to be transferred.
Snapshots created by the remote replication process are a special form called replication snapshots, which
do not count against snapshot license limits.
In order to perform a replication, a snapshot of the primary volume is taken, creating a point-in-time image
of the data. This point-in-time image is then replicated to the secondary volume by copying the data
represented by the snapshot using a transport medium such as TCP/IP (iSCSI) or Fibre Channel. The first
replication copies all data from the primary volume to the secondary volume; subsequent replications use
sparse snapshots.
Replication snapshots are retained for both the primary volume and the secondary volume. When a
matching pair of snapshots is retained for both volumes, the matching snapshots are referred to as
replication sync points. The two snapshots (one on each volume) are used together as a synchronization
reference point, minimizing the amount of data to transfer. The two snapshots in a sync point are assigned
the same image ID, which uniquely identifies that the data in those snapshots are from the same
point-in-time image and are block-for-block identical.
When a replication snapshot is created from a standard snapshot, while that snapshot remains present the
replication snapshot's total data represented is zero bytes. This behavior occurs because the snapshot data
remains associated with the standard snapshot and there is no data specifically associated with the
replication snapshot. If the standard snapshot is deleted, its data becomes associated with (is preserved
by) the replication snapshot and the replication snapshot's size changes to reflect the size of the deleted
snapshot.
An added benefit of using snapshots for replication is that these snapshots can be kept and restored later
in the event of a non-hardware failure, such as virus attack. Since the replication source is a snapshot, any
writes performed on the primary volume after the snapshot is taken are not replicated by that task. This
gives you more control over what is contained in each replication image.
108 Using Remote Snap to replicate volumes
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