PrimeArray 4xxx, User Manual

Page: 129 / 208

Snapshot – Fast Point-In-Time Copies
Chapter 9 Backup and Recovery
9.1 Snapshot – Fast Point-In-Time Copies
Snapshots are read-only copies of file-systems at a specific
point in time. Snapshot distinguishes itself in its speed. Creating
a snapshot is not involved with copying user data, thus usually
taking less than a second.
The concept of snapshot is very different from tape backups.
Data are not copied to any media during backup. Instead, it
just informs the NAS that all the data blocks in use should be
preserved, not being overwritten. That is why it can be so fast.
The “copy” occurs during everyday file access. When a file is
modified after a snapshot is created, its original data blocks
are protected from being overwritten. The new updates are
written to a new location. The file-system maintains records
and pointers to keep track of the snapshot data and file
changes.
The snapshot feature is activated by default on model
4400/4420/8400/8420. It is an optional feature on model
4100/4200/8100/8200.
Snapshot Management
To manage snapshots, please open the administration page.
Enter the Backup Snapshot Manage page and select a
volume.
Viewing Snapshot Information
On the page shows the snapshots existing on the volume and
their information.
Snapshot Used Space indicates the disk
space used by snapshot data. In the table – List of Snapshots ,
Space to Free indicates the disk space which will be freed if a
Chapter 9
119