Configuration: premium, Feature—snapshot virtual disks – Dell POWERVAULT MD3600F User Manual

Page 145

Advertising
background image

Configuration: Premium Feature—Snapshot Virtual Disks

145

10

Configuration: Premium Feature—

Snapshot Virtual Disks

NOTE:

If you ordered this feature, you received a Premium Feature 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.

NOTE:

The snapshot feature allows up to 16 snapshots per LUN and 256 per array

to be present at the same time.

A snapshot virtual disk is a point-in-time image of a virtual disk in a storage

array. It is not an actual virtual disk containing a copy of the original data; it is

a reference to the data that was contained on a virtual disk at a specific time.

A snapshot virtual disk is the logical equivalent of a complete physical copy.

However, you can create a snapshot virtual disk much faster than a physical

copy, using less disk space.
The virtual disk on which the snapshot is based, called the source virtual disk,

must be a standard virtual disk in your storage array. Typically, you create a

snapshot so that an application, such as a backup application, can access the

snapshot and read the data while the source virtual disk remains online and

accessible.

NOTE:

No I/O requests are permitted on the source virtual disk while the virtual

disk snapshot is being created.

A snapshot repository virtual disk containing metadata and copy-on-write

data is automatically created when a snapshot virtual disk is created. The only

data stored in the snapshot repository virtual disk is that which has changed

since the time of the snapshot.
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

book.book Page 145 Tuesday, June 18, 2013 3:03 PM

Advertising
This manual is related to the following products: