Shadow Copy Planning; Identifying The Volume - HP StoreEasy 1000 Storage Administrator's Manual

The Volume Shadow Copy Service provides an infrastructure for creating point-in-time snapshots
(shadow copies) of volumes. Shadow Copy supports 64 shadow copies per volume.
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 add-on program,
which enables them to view the file in Windows Explorer. Accessing previous versions of files, or
shadow copies, enables users to:
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?

Identifying the volume

Shadow copies are taken for a complete volume, but not for a specific directory. Shadow copies
work best when the server stores user files, such as documents, spreadsheets, presentations,
graphics, or database files.
NOTE: Shadow copies should not be used to provide access to previous versions of application
or e-mail databases.
Shadow copies are designed for volumes that store user data such as home directories and My
Documents folders that are redirected by using Group Policy or other shared folders in which users
store data.
Shadow copies work with compressed or encrypted files and retain whatever permissions were
set on the files when the shadow copies were taken. For example, if a user is denied permission
to read a file, that user would not be able to restore a previous version of the file, or be able to
read the file after it has been restored.
Volume shadow copies 63