Dell PowerVault MD3820f - Manual (Page 174)

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.
Scheduling A Snapshot Virtual Disk
When you create a snapshot virtual disk, you can choose whether the snapshot is created immediately or
is created according to a schedule that you determine. This schedule can be a one-time snapshot
creation or an snapshot creation that occurs at regularly occurring intervals. If a schedule is not specified,
the snapshot virtual disk creation happens immediately upon execution of the command.
A schedule can be specified when a snapshot virtual disk is first created, or it can be added to an existing
snapshot virtual disk at any time. One schedule per snapshot virtual disk is supported.
Common Reasons For Scheduling A Snapshot Virtual Disk
Scheduling a snapshot virtual disk can serve multiple purposes across a data storage environment. Most
common uses of a snapshot scheduler are:
• Data backups
• Rapid recovery from a data loss event
A scheduled data backup can protect against data loss on a regular, unmonitored basis. For example, if an
application stores business-critical data on two virtual disks in the storage array, you may choose to
perform an automatic backup every day. To implement this backup, select the first virtual disk and create
a backup schedule that runs once a day, Monday through Friday, at a time between the end of the work
day and 11PM. Do not select an end date. Apply the same schedule to the second virtual disk, then map
the two snapshot virtual disks to your backup host server and perform your regular backup procedures.
Remember to unmap the two resulting snapshot virtual disks before the next scheduled snapshot begins.
If the snapshot virtual disks are not unmapped, the storage array does not perform the next scheduled
snapshot operation in order to avoid data corruption.
Scheduled snapshots are also valuable in the event of a data loss. For example, if you back up your data at
the end of every work day and keep hourly snapshots from 8AM to 5PM, data can be recovered from the
snapshots in windows smaller than one hour. To accomplish this type of rapid recovery, create a
schedule that contains a start time of 8AM and an end time of 5PM, then select 10 snapshots per day on
Monday through Friday with no end date.
Guidelines for Creating Snapshot Schedules
Certain guidelines apply when creating snapshot virtual disk schedules:
• Scheduled virtual disk snapshot operations do not occur if:
– The snapshot virtual disk is mapped
– The storage array is offline or turned off
– The snapshot virtual disk is in use as a source virtual disk during a Virtual Disk Copy operation
– A copy operation is Pending or In progress
• Deleting a snapshot virtual disk that contains a schedule also deletes the schedule.
• Snapshot schedules are stored in the configuration database on the storage array. The Management
Station does not need to be running for scheduled snapshot operations to occur.
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