HP StorageWorks 8000 - NAS Overview page 7

Directories
Directories let you organize information. Directories contain files or other persistent data
structures in a file system that contains information about other files. Directories are usually
organized hierarchically and may contain both files and other directories, and are used to
organize collections of files for applications or convenience.
Snapshots
Snapshots are an important part of data-protection plans. A good data-protection plan should
include a backup strategy, storage redundancy provided by RAID levels, and snapshots.
Snapshots provide nearly instantaneous access to previous versions of a file stored on the HP
NAS 8000 HA solution.
A snapshot is a read-only picture of a file volume at a specific point in time. When you create
a snapshot of a file volume, the snapshot initially consumes zero physical space. However, as
users modify the file volume, the snapshot tracks changes between the original file volume and
the modified file volume. If an error occurs and a user needs to revert to the previous version,
the snapshot version of the file can be restored.
Snapshots consume storage space. When planning storage, consider how dynamic your data
will be. With file volumes in which data changes rapidly, snapshots will consume a larger
amount of space. At the extreme limit, a file volume can change so much from the original
information that the snapshot consumes the same amount of space as the original data.
Typically, data does not change so rapidly, and the usage and growth of snapshot space is
relatively slow.
Snapshots are optional and may be created at any time after the basic storage configuration is
complete. Users can add or resize a snapshot at a later time if there is enough free space
available in the volume group.
Network and Storage Planning 7