HP P6000 Replication Solutions Manager User Guide (T3680-96089, October 2012)

Write cache setting after replicationFlush implementationMethod
You must include job commands to set the source
disk to write-through mode and wait for the flush
to complete before starting the replication.
Job preallocated copy (converted container) to
write-back mode.
If you want the source disks or copies to be in
write-through mode, you must explicitly set them.
You must issue CLUI commands to set the source
disk to write-through mode and wait for the flush
to complete before starting the replication.
CLUI
This feature is controller software version dependent. See Controller software features - local
replication. See also virtual disk Containers.
Snapshot FAQ
• How can I tell a snapshot from other types of virtual disks?
Because snapshots are not independent virtual disks, they are identified differently than original
(active) virtual disks. See virtual disks Types.
• How long does it take to create a snapshot?
A snapshot requires only a matter of seconds, no matter how large the original (active) virtual
disk.
• If it is virtual, can a host write to a snapshot?
Yes. A snapshot is functionally equivalent to a physical disk with both read and write capability.
• After I create a snapshot, can I delete the original (active) virtual disk?
No. A snapshot always relies, at least in part, on the original (active) virtual disk for data. If
the original virtual disk is deleted, its associated snapshot becomes unusable. A snapshot
should be thought of as a temporary copy.
• Can I make multiple snapshots of an original (active) virtual disk?
Yes. However, there is a limit. See virtual disks Snapshot guidelines.
• What is the maximum number of snapshots on a storage system?
There is no limit. However, the greater the number of snapshots, the longer it takes to shut
down the storage system during maintenance and upgrade activities.
• Can I create a snapshot of a snapclone?
Yes.
• Can I create an snapshot of a snapshot?
No.
Snapshot guidelines
The following guidelines apply to snapshot virtual disks:
• The array must have a local replication license. See Replication licenses overview.
• The maximum number of snapshots per source varies with controller software versions. See
Controller software features - local replication.
• A snapshot is always created in the same disk group as the source virtual disk.
• The redundancy level (Vraid) of a snapshot must be the same or lower than the source. See
Redundancy level (Vraid).
• All snapshots of the same virtual disk must be the same type (demand allocated or fully
allocated) and redundancy level. See Snapshot types (allocation policy).
272 Virtual disks