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144 Configuration: Premium Feature—Snapshot Virtual Disks
After the snapshot repository virtual disk is created, I/O write requests to the
source virtual disk resume. Before a data block on the source virtual disk is
modified, the contents of the block to be modified are copied to the snapshot
repository virtual disk for safekeeping. Because the snapshot repository virtual
disk stores copies of the original data in those data blocks, further changes to
those data blocks write only to the source virtual disk. The snapshot
repository uses less disk space than a full physical copy, because the only data
blocks that are stored in the snapshot repository virtual disk are those that
have changed since the time of the snapshot.
When you create a snapshot virtual disk, you specify its location, capacity,
and other parameters. You can disable or delete the snapshot virtual disk
when it is not required. If you disable a snapshot virtual disk, you can re-
create and reuse it the next time you perform a backup. For more
information, see "Re-creating Snapshot Virtual Disks" on page 157. If you
delete a snapshot virtual disk, you also delete the associated snapshot
repository virtual disk.
NOTE: Deleting a snapshot does not affect data on the source virtual disk.
NOTE: The following host preparation sections also apply when using the snapshot
feature through the CLI interface.
Creating a Snapshot Virtual Disk Using the
Simple Path
You can choose the simple path to create a snapshot virtual disk if the disk
group of the source virtual disk has the required amount of free space. A
snapshot repository virtual disk requires a minimum 8 MB of free capacity.
The destination of a snapshot repository virtual disk is determined based on
the free capacity available in the disk group.
If 8 MB of free capacity is not available in the disk group of the source virtual
disk, the Create Snapshot Virtual Disks feature defaults to the advanced path.
For more information, see "Creating a Snapshot Virtual Disk Using the
Advanced Path" on page 148.
In the advanced path option, you can choose to place the snapshot repository
virtual disk in another disk group or you can use unconfigured capacity on the
storage array to create a new disk group.
book.book Page 144 Wednesday, June 8, 2011 5:01 PM