Dell PowerVault MD3820f - Manual (Page 178)

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. See
Creating A Snapshot Virtual Disk Using The
Advanced Path .
NOTE: You can create concurrent snapshots of a source virtual disk on both the source disk group
and on another disk group.
Before creating a Snapshot Virtual Disk, note that:
• The following types of virtual disks are not valid source virtual disks:
– Snapshot repository virtual disks
– Snapshot virtual disks
– Target virtual disks that are participating in a virtual disk copy
• You cannot create a snapshot of a virtual disk that contains unreadable sectors.
• You must satisfy the requirements of your host operating system for creating snapshot virtual disks.
Failure to meet the requirements of your host operating system results in an inaccurate snapshot of
the source virtual disk or the target virtual disk in a virtual disk copy.
NOTE: Before you create a new snapshot of a source virtual disk, stop any data access (I/O)
activity or suspend data transfer to the source virtual disk to ensure that you capture an accurate
snapshot of the source virtual disk. Close all applications, including Windows Internet Explorer,
to make sure all I/O activity has stopped.
NOTE: Removing the drive letter of the associated virtual disk(s) in Windows or unmounting the
virtual drive in Linux helps to guarantee a stable copy of the drive for the Snapshot.
Before creating a snapshot virtual disk, the host server must be in the proper state. To prepare your host
server:
1. Stop all I/O activity to the source.
2. Using your Windows system, flush the cache to the source. At the host prompt, type SMrepassist
-f <filename-identifier> and press <Enter>. For more information, see SMrepassist Utility .
3. Remove the drive letter(s) of the source in Windows or unmount the virtual drive(s) in Linux to help
guarantee a stable copy of the drive for the Snapshot.
If this is not done, the snapshot operation reports that it has completed successfully, but the
snapshot data is not updated properly.
NOTE: To verify that the virtual disk is in Optimal or Disabled state, select the Summary tab and
then click Disk Groups & Virtual Disks.
The Create Snapshot Virtual Disk Wizard - Introduction dialog is displayed.
4. Follow any additional instructions for your operating system. Failure to follow these additional
instructions can create unusable snapshot virtual disks.
NOTE: If your operating system requires additional instructions, you can find those instructions
in your operating system documentation.
After your host server has been prepared, see Creating A Snapshot Virtual Disk Using The Advanced
Path , to create the snapshot using the advanced path.
If you want to use a snapshot regularly, such as for backups, use the Disable Snapshot and Re-create
Snapshot options to reuse the snapshot. Disabling and re-creating snapshots preserves the existing
virtual disk-to-host mappings to the snapshot virtual disk.
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