HP ProLiant Storage Server User Guide (440584-003, September 2007)

of snapshots is the abilit y to instantly recover data from shad ow 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 separat

e 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 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-ma il

databases.

Shadow copies are designed for volumes that store user data such as home directories and My D ocuments

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 ﬁle, or be able to read the ﬁle af ter

it has been restored.

Although shadow copies are taken for an entire volume, users must use shared folders to access sha dow

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 ﬁrstsharethefolder.

NOTE:

Shadow copies are available o nly on NTFS, not FAT or FAT32 volum es.

Files or folders that are recorded by using Shadow Copy appear static, even though the original d ata is

changin

Allocating disk space

When determining the amount of space to allocate for storing shadow co pies, consider both the number

and size of ﬁles that are being c opied, 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 exp ectations of how many versions they will want to have

available. End users might expect only a single shadow c opy to be available, or they might expect three

days or three weeks worth of shadow copies. The more shadow copies users expect, the m ore storage

space a dministrators 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.

HP ProLiant Storage Server