Snapclone faq, Preallocated snapclones – HP P6000 Continuous Access Software User Manual
Page 270
The snapclone property indicates whether a virtual disk can be locally replicated using the snapclone
method. Values are:
•
Yes. The virtual disk complies with snapclone guidelines. Snapclone replication can be
performed.
•
No. The virtual disk does not comply with snapclone guidelines. Snapclone replication cannot
be performed.
Preallocated snapclones
Preallocated snapclone refers to a snapclone that is created by copying data from a source virtual
disk to a container and immediately converting the container into a virtual disk. Compared to a
standard snapclone, creating a preallocated snapclone is faster. In cases where host I/O must be
suspended, the improved speed of preallocated snapclones reduces the time that a host application
is suspended.
When a preallocated snapclone is created, the source virtual disk write cache must be flushed
before replication is started. (See cache policies
.) This ensures that the source virtual
disk and snapclone copy contain identical data. The following table shows how a write cache
flush is implemented.
IMPORTANT:
When using jobs or the CLUI, you must explicitly ensure that write caches are
flushed.
Write cache setting after replication
Flush implementation
Method
When replication is complete, the controller
software automatically sets the source disk and
The replication manager automatically sets the
source disk to write-though mode and ensures the
flush has completed before starting the replication.
GUI action
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 include job commands to set the source
disk to write-through mode and wait for the flush
to complete before starting the replication.
Job
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
. See also virtual disk
Snapclone FAQ
•
How can I tell a snapclone from other types of virtual disks?
Because snapclones are independent virtual disks, they are identified as original (active) virtual
disks. This distinguishes them from snapshots, but not from other independent virtual disks.
See virtual disks
.
•
How long does it take to create a snapclone?
A snapclone requires only a matter of seconds to create, no matter how large the source.
However, the snapclone does not become an independent virtual disk until unsharing is
completed.
•
What is snapclone normalization or unsharing?
Normalization or unsharing is a snapclone background process. See virtual disks
270 Virtual disks