•You cannot extend striped volumes, mirrored volumes, or RAID 5 volumes. For more information, see the Disk Management online help.
Volume shadow copies
NOTE:
Select storage systems can be deployed in a clustered as well as a
The Volume Shadow Copy Service provides an infrastructure for creating
A shadow copy contains previous versions of the files or folders contained on a volume at a specific point in time. While the shadow copy mechanism is managed at the server, previous versions of files and folders are only available over the network from clients, and are seen on a per folder or file level, and not as an entire volume.
The shadow copy feature uses data blocks. As changes are made to the file system, the Shadow Copy Service copies the original blocks to a special cache file to maintain a consistent view of the file at a particular point in time. Because the snapshot only contains a subset of the original blocks, the cache file is typically smaller than the original volume. In the snapshot's original form, it takes up no space because blocks are not moved until an update to the disk occurs.
By using shadow copies, a storage system can maintain a set of previous versions of all files on the selected volumes. End users access the file or folder by using a separate client
•Recover files that were accidentally deleted. Previous versions can be opened and copied to a safe location.
•Recover from accidentally overwriting a file. A previous version of that file can be accessed.
•Compare several versions of a file while working. Use previous versions to compare changes between two versions of a file.
Shadow copies cannot replace the current backup, archive, or business recovery system, but they can help to simplify restore procedures. Because a snapshot only contains a portion of the original data blocks, shadow copies cannot protect against data loss due to media failures. However, the strength of snapshots is the ability to instantly recover data from shadow copies, reducing the number of times needed to restore data from tape.
Shadow copy planning
Before setup is initiated on the server and the client interface is made available to end users, consider the following:
•From what volume will shadow copies be taken?
•How much disk space should be allocated for shadow copies?
•Will separate disks be used to store shadow copies?
•How frequently will shadow copies be made?
P4000 G2 Unified NAS Gateway User Guide 73
