HP LeftHand P4000 Virtual SAN Appliance Software - Manual (Page 10)

Using schedules for Remote Copy
Scheduled remote snapshots provide fault tolerance for business continuance and disaster recovery,
and a consistent, predictable update of data for remote backup and recovery.
Planning the Remote Copy schedule
Planning is critical. The following issues impact the amount of storage available in the system:
•
Recurrence
•
Capacity
•
Retention
Recurrence
How often do you want the snapshots created? The recurrence frequency must account for the
amount of time it takes to complete a remote snapshot. For example, if your recurrence schedule
is set for a new snapshot every four hours, you should ensure that the time to copy that snapshot
to the remote location is less than four hours.
Testing the copy time
One way to check the time required to copy a snapshot is to run a test of the actual process. To
test this process, take two remote snapshots of the primary volume. Because the first remote snapshot
copies the entire volume, it takes longer to copy. The second remote snapshot copies only changes
made to the volume since the first remote snapshot was taken. You create the second remote
snapshot after the time interval you intend to schedule. Because of that, the copy time for the second
remote snapshot is more representative of the actual time required for copying subsequent remote
snapshots.
To test the copy time:
1. Create a remote snapshot of the primary volume.
2. Wait for the copy to finish.
3. Create another remote snapshot of the primary volume.
4. Track the time required to complete the second remote snapshot.
NOTE: This is the minimum amount of time that you should allow between scheduled copies.
5. Check the remote bandwidth setting for the other management group by using the Edit
Management Group
command. This setting affects the time required to copy a remote
snapshot.
Capacity
Does the cluster that contains the remote volume have sufficient space to accommodate scheduled
snapshots?
If the cluster does not have sufficient space available, the remote snapshot appears in the CMC
and flashes red. On the Details tab of the remote snapshot, the status message displayed is Read
only, not enough space in cluster to start copy.
Retention policies
How long do you want to retain the primary snapshots? The remote snapshots? You can set different
retention policies for the primary and remote snapshots. For example, you can choose to retain
two primary snapshots and five remote snapshots. The number of snapshots retained refers to
10 Understanding and planning Remote Copy