Replication Actions - HP P2000 G3 Reference Manual

NOTE: Because replication is not synchronous (continuous), data in a secondary volume is only as current
as the last replication that completed successfully. Replications can be performed manually or scheduled.
Snapshot operations are I/O-intensive. Every write to a unique location in a master volume after a
snapshot is taken will cause an internal read and write operation to occur in order to preserve the snapshot
data. If you intend to create snapshots of, create volume copies of, or replicate volumes in a vdisk, ensure
that the vdisk contains no more than four master volumes, snap pools, or both. For example: 2 master
volumes and 2 snap pools; 3 master volumes and 1 snap pool; 4 master volumes and 0 snap pools.

Replication actions

The following figure illustrates actions that occur during a series of replications from System 1 to System 2.
1 Take initial snapshot and initiate replication.
2 Initial replication consists of a full data copy.
3 Take second snapshot and request replication. This
can be taken while the initial replication is in progress.
4 Snapshot taken on secondary volume. This is the first
replication sync point.
5 When the initial replication is complete, the second
replication automatically starts. Only the data
changed since Snap 1 is replicated.
Figure 5 Actions that occur during a series of replications
The figure above illustrates initial, delta, and queued replications:
• Initial replication: When the first replication is initiated, a snapshot of the primary volume is taken and
every block of data is then copied to the secondary volume. When the copy is complete, the first
snapshot is taken on the secondary volume, creating the first sync point. This sync point can be used to
determine the delta data from that sync point to a later snapshot. Actions 1–4 are the initial replication.
6 Second snapshot taken on secondary volume. This is
the second sync point.
7 Other snapshots can be taken and replication initiated
on the primary volume while replication is in progress.
These snapshots are queued waiting for prior
replications to complete. These replication snapshots
will not become sync points until their replications are
complete.
HP StorageWorks P2000 G3 MSA System SMU Reference Guide 107