Implementing off-host point-in-time copy solutions

Figure: Example implementation of an off-host point-in-time copy solution 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).

Figure: Example implementation of an off-host point-in-time copy solution

Example implementation of an off-host point-in-time copy solution

Also, if you place the snapshot volumes on disks that are attached to host controllers other than those for the disks in the primary volumes, it is possible to avoid contending with the primary host for I/O resources. To implement this, paths 1 and 2 shown in the Figure: Example implementation of an off-host point-in-time copy solution should be connected to different controllers.

Figure: Example connectivity for off-host solution using redundant-loop access shows an example of how you might achieve such connectivity using Fibre Channel technology with 4 Fibre Channel controllers in the primary host.

Figure: Example connectivity for off-host solution using redundant-loop access

Example connectivity for off-host solution using redundant-loop access

This layout uses redundant-loop access to deal with the potential failure of any single component in the path between a system and a disk array.

Note:

On some operating systems, controller names may differ from what is shown here.

Figure: Example implementation of an off-host point-in-time copy solution using a cluster node shows how off-host processing might be implemented in a cluster by configuring one of the cluster nodes as the OHP node.

Figure: Example implementation of an off-host point-in-time copy solution using a cluster node

Example implementation of an off-host point-in-time copy solution using a cluster node

Figure: Example implementation of an off-host point-in-time copy solution using a separate OHP host shows an alternative arrangement, where the OHP node could be a separate system that has a network connection to the cluster, but which is not a cluster node and is not connected to the cluster's private network.

Figure: Example implementation of an off-host point-in-time copy solution using a separate OHP host

Example implementation of an off-host point-in-time copy solution using a separate OHP host

Note:

For off-host processing, the example scenarios in this document assume that a separate OHP host is dedicated to the backup or decision support role. For clusters, it may be simpler, and more efficient, to configure an OHP host that is not a member of the cluster.

Figure: Implementing off-host processing solutions illustrates the steps that are needed to set up the processing solution on the primary host.

Figure: Implementing off-host processing solutions

Implementing off-host processing solutions

Disk Group Split/Join is used to split off snapshot volumes into a separate disk group that is imported on the OHP host.

Note:

As the snapshot volumes are to be moved into another disk group and then imported on another host, their contents must first be synchronized with the parent volumes. On reimporting the snapshot volumes, refreshing their contents from the original volume is speeded by using FastResync.