Dell PowerVault MD3420 - Manual (Page 69)

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Using The Snapshot (Legacy) Feature
The following types of virtual disk snapshot premium features are supported on the MD storage array:
• Snapshot Virtual Disks using multiple point-in-time (PiT) groups
• Snapshot Virtual Disks (Legacy) using a separate repository for each snapshot
NOTE: This section describes the Snapshot Virtual Disk (legacy) premium feature. If you are using
the Snapshot Virtual Disk using PiT groups, see
Using The Snapshot Feature .
This chapter describes how the Snapshot (legacy) feature works, lists the snapshot script commands, and
explains how to use the commands to create snapshot virtual disks. Additional information about the
Snapshot (legacy) feature and related definitions is available in the online help, the Deployment Guide,
the MD Storage Manager online help, and the Owner’s Manual.
The Snapshot (legacy) feature creates a snapshot virtual disk that you can use as a backup of your data.
A snapshot virtual disk is a logical point-in-time image of a standard virtual disk. Because it is not a
physical copy, a snapshot virtual disk is created more quickly than a physical copy and requires less
physical disk space. Typically, you create a snapshot virtual disk so that an application, such as a backup
application, can access the snapshot virtual disk. The application reads the data while the source virtual
disk remains online and user accessible. You can also create several snapshot virtual disks of a source
virtual disk and write data to the snapshot virtual disks to perform testing and analysis.
NOTE: If you ordered Premium Features for the Snapshot Virtual Disks, you would have received a
Premium Features Activation card shipped in the same box as your Dell PowerVault MD storage
array. Follow the directions on the card to obtain a key file and to enable the feature. For more
information, see Premium Feature — Snapshot Virtual Disks in the Owner’s Manual.
Snapshot virtual disks allow you to perform the following tasks:
• Create a complete image of the data on a source virtual disk at a particular point in time.
• Use only a small amount of disk space.
• Provide quick, frequent, nondisruptive backups; or test new versions of a database system without
affecting actual data.
• Provide for snapshot virtual disks to be read, written, and copied.
• Use the same availability characteristics of the source virtual disk (such as redundant array of
independent disks (RAID) protection and redundant path failover).
• Map the snapshot virtual disk and make it accessible to any host on a storage area network. You can
make snapshot data available to secondary hosts for read and write access by mapping the snapshot
to the hosts.
• Create up to four snapshots per virtual disk.
NOTE: The maximum number of snapshot virtual disks is one-half of the total number of virtual
disks supported by the RAID controller module.
• Increase the capacity of a snapshot virtual disk.
The following table lists the components that comprise a snapshot virtual disk and briefly describes what
they do.
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