HP StorageWorks SAN Virtualization Services Platform Manager User Guide (5697-0454, May 2010)

16 Using snapclones
The snapclone service enables you to create multiple physical copies of any Virtualization Services
Manager (VSM) virtual disk or snapshot. The snapclone process is carried out without any use of host
resources. Each copy can be made independently accessible and instantly available for both read
and write operations, even while being created. Applications can immediately start using the copies
while a snapclone continues to move the data in the background with no need to wait for the operation
to complete.
Multiple copies of the same source virtual disk can exist at any time and can be assigned to different
hosts for applications such as backup, testing, and decision support. The copies are presented to
applications as regular virtual disks. The creation of each snapclone of a single source virtual disk is
an independent procedure.
The snapclone service features:
• Snapclone operations both within and across domains.
• The ability to create a maximum of 64 copies of one virtual disk at any one time.
• Independent host permissions to different copies.
• Multiple copies made at different points in time.
• Instant availability. Host applications can start using copies immediately after the snapclone process
begins, with no need to wait for the snapclone process to be completed.
The snapclone service enables you to create:
• Snapclone groups—A snapclone group defines a source element to be copied. A source element
may be a virtual disk, a VDG, a snapshot, or a VDG snapshot. When you create a snapclone
group, a snapshot PiT is created on the source element. The PiT is maintained until all snapclone
tasks on the group finish.
• Snapclone tasks—A snapclone task is a process that copies the PiT created on the source element
of a snapclone group to a specified destination. One initial task is automatically created when
you create a group and begins immediately after group creation. You can then define additional
tasks to snapclone the source element to additional destinations.
When each snapclone task finishes, the task is deleted automatically. When all tasks are complete,
the group is also deleted. You can suspend, resume, and delete tasks at any time.
You can optionally assign hosts permission to a destination virtual disk even while the task is in process.
If you do this, the permitted host is initially presented with a snapshot of the PiT that is created for the
group. While the task copies the PiT to the destination, the host’s modifications are written to the
snapshot. When the snapcloning of the PiT is complete, the modifications accumulated on the snapshot
are resynchronized into the destination PiT, creating the final destination virtual disk. The task is then
complete.
If you do not assign host permission when you define a task, you can assign host permission to the
destination virtual disk after the task is completed.
Assigning host permission at the task creation stage is only supported for snapclone tasks within the
local domain.
Snapclones can be used in the following implementations:
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