Adaptec 5325301638 - Snap Server 4500 NAS, Administrator'S Manual

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Snapshot Management and Usage
56 Snap Server Administrator Guide
snapshot and clicking the
Rollback
button. During the rollback operation, data on
the volume will be inaccessible to clients.
Cautions
(1) Rolling back a volume cannot be undone and should only be used as a last
resort after attempts to restore selected directories or files have failed; (2) Performing a
rollback on a volume may invalidate the NetVault for GuardianOS nvdb directory for
the volume, and may also disable the antivirus software. If you are using these features,
take the necessary precautions as described in “Volumes” on page 33.
Scheduling Snapshots
Snapshots should ideally be taken when your system is idle. It is recommended that
snapshots be taken before a backup is performed. For example, if your backup is
scheduled at 4am, schedule the snapshot to be taken at 2am, thereby avoiding
system activity and ensuring the snapshot is backed-up. See “Coordinating
Snapshot and Backup Operations” on page 59 for more information.
Snapshots and Backup Optimization
When you back up a live volume directly, files that reference other files in the
system may become “out-of sync” in relation to each other. The more data you have
to back up, the more time is required for the backup operation, and the more likely
these events are to occur. By backing up the snapshot rather than the volume itself,
you greatly reduce the risk of archiving inconsistent data. For instructions, see
“Coordinating Snapshot and Backup Operations” on page 59.
NDMP and Snapshots
A snapshot is automatically initiated by this type of backup operation.
Administrators backing up via NDMP should consider the following:
• When files and directories on a Windows SnapTree are backed up and restored
to a UNIX SnapTree, extended Windows attributes and file ownership are not
preserved.
• If the snapshot pool does not have sufficient space to fire an additional
snapshot, it will remove the oldest snapshots to create the space required.
• NDMP backup jobs may not time out for extended periods when interrupted
or the NDMP service is stopped. The DMA will continue to attempt to write
data to the target device.
Snapshots and iSCSI Disks
Running a snapshot on a volume containing an iSCSI Disk will abruptly disconnect any
clients attempting to write to the iSCSI Disk and the resulting snapshot may contain
inconsistent data. Do not use snapshots on a volume containing an iSCSI Disk.