Specifications
Using Snapshots
Chapter 6 Data Protection 99
Recurring Snapshots
A recurring Snapshot runs according to a schedule you specify. A recurring
Snapshot schedule works like a log file rotation, where a certain number of recent
Snapshots are automatically generated and retained as long as possible, after which
the oldest Snapshot is discarded.
Managing the Snapshot Pool
Snapshots are stored on a RAID in a Snapshot pool, or space reserved within the
RAID for this purpose. Each RAID may contain only one Snapshot pool, which
contains all Snapshots of all volumes on the RAID.
Snapshots grow dynamically for as long as they are active and as long as there is
enough space available in the Snapshot pool to store them. When the Snapshot pool
approaches its capacity (at about 95%), the Snap Server deletes the oldest Snapshot
to create space for more recent Snapshots.
The default configuration allots 80% of RAID capacity to the volume and 20% to the
Snapshot pool. You can adjust the size of the pool up or down according to your
needs. If Autodeletion removes older Snapshots more frequently than your backup
strategy allows, consider increasing Snapshot pool capacity.
The number of Snapshots that the Snap Server can support is a function of: (1) the
space reserved for the Snapshots; (2) the duration of the Snapshots you create; and,
(3) the amount and type of write activity to the volume(s) since the Snapshot was
created. The following table describes minimum and maximum allocation cases.
To Adjust Snapshot Pool Capacity
1
Navigate to the
Storage > Snapshots
screen, and click the
adjust snapshot space
link in the introductory text.
2
In the screen that opens, type a new number for the volume for which you want
to increase or decrease Snapshot space.
3
Click
Save
.
Allocate about 5% of RAID if Allocate about 25% of RAID if
• Activity is write-light
• Write access patterns are concentrated in
a few places
• Snapshots need not remain available for
long periods
• Activity is write-heavy
• Write access patterns are randomized
across the volume
• Snapshots must remain available for long
periods