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.
Although shadow copies are taken for an entire volume, users must use shared folders to access
shadow copies. Administrators on the local server must also specify the
\\servername\
sharename
path to access shadow copies. If administrators or end users want to access a previous
version of a file that does not reside in a shared folder, the administrator must first share the folder.
NOTE:
Shadow copies are available only 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 changing.
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.
Administrators should also consider user expectations of how many versions they will want to have
available. End users might expect only a single shadow copy to be available, or they might expect
three days or three weeks worth of shadow copies. The more shadow copies users expect, the
more storage space administrators must allocate for storing them.
Setting the limit too low also affects backup programs that use shadow copy technology because
these programs are also limited to using the amount of disk space specified by administrators.
NOTE:
Regardless of the volume space that is allocated for shadow copies, there is a maximum
of 64 shadow copies for any volume. When the 65th shadow copy is taken, the oldest shadow
copy is purged.
The minimum amount of storage space that can be specified is 350 megabytes (MB). The default
storage size is 10 percent of the source volume (the volume being copied). If the shadow copies
are stored on a separate volume, change the default to reflect the space available on the storage
Volume shadow copies
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