HP ProLiant ML350 G5 Storage Server Administration Guide (5697-5854, September 2006)

• Recover from accidentally overwriting a file. A previous version of that file can be acc essed.
• 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 can not 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 ser ver 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 separ
ate disks be used to store shadow c opies?
• How frequently will shadow copies be made?
Identifying the volume
Shadow copies are taken for a complete volume, but not for a specificdirectory. Shadowcopies
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 P olicy 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 fi le, or be able to read the file after
it has been restored.
Although shadow copies are taken for an entire volume, users must use shared folders to access shadow
copies. Administrators on the loc a l server must also specify the \\servername\sharename path to
access shadow copies. If administrators or end users want to access a prev i ous version of a file that does
not reside in a shared folder, the administrator must firstsharethefolder.
NOTE:
Shadow copies are available o nly on NTFS, not FAT or FAT32 volumes.
Files or folders that are recorded by using Shadow Copy appear static, even though the original data is
changi
ng.
Allocating disk space
When determining the amount of space to allocate for storing shadow copies, consider both the number
and size of files that are being copied, as well as the frequency of changes between copies. For
example, 100 files that only change monthly require less storage space than 10 files that change daily. If
the frequency of changes to each file is greater than the amount of space allocated to storing shadow
copies, no shadow copy is created.
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