Veritas FlashSnap Point-In-Time Copy Solutions 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009

Figure 1-2
Example point-in-time copy solution on a primary host
Disks containing primary
volumes used to hold
production databases or file
systems
Disks containing synchronized
full-sized instant snapshot
volumes
Primary host
1 2
SCSI or Fibre
Channel connectivity
In this setup, it is recommended that separate paths (shown as 1 and 2) from
separate controllers be configured to the disks containing the primary volumes
and the snapshot volumes. This avoids contention for disk access, but the primary
host’s CPU, memory and I/O resources are more heavily utilized when the
processing application is run.
Note: For space-optimized or unsynchronized full-sized instant snapshots, it is
not possible to isolate the I/O pathways in this way. This is because such snapshots
only contain the contents of changed regions from the original volume. If
applications access data that remains in unchanged regions, this is read from the
original volume.
Implementing off-host point-in-time copy solutions
Figure 1-3 illustrates that, by accessing snapshot volumes from a lightly loaded
host (shown here as the OHP host), CPU- and I/O-intensive operations for online
backup and decision support are prevented from degrading the performance of
the primary host that is performing the main production activity (such as running
a database).
19Point-in-time copy solutions
Implementing off-host point-in-time copy solutions