Swvr Lifeguard Service; Default Settings - Compaq N2400 - TaskSmart - 1 GB RAM Administration Manual

SWVR Lifeguard Service

SWVR Lifeguard is a utility that watches storage pools for pool-full
conditions and deletes snapshots when a pool is nearly full. Pool-full
conditions cause writes to the drive to be delayed. These conditions can occur
when snapshots are being used and insufficient space is left in the pool to
allow copying the data from the original virtual disk to the snapshot. If this
situation occurs, the system delays the write to both the original virtual disk
and the snapshot.
Because snapshots utilize free space in the pool, a pool-full condition can be a
result of poor or improper pool space planning. Make sure there is sufficient
space for snapshots. By default, 30 percent of the pool space is reserved for
snapshots.
If you attempt to use a snapshot to restore your virtual disk, special care must
be taken to make sure there is sufficient free space in the pool. The newly
restored virtual disk is created from available free pool space. If there is
insufficient space to create the new drive, the restore will fail. However, even
if there is just enough space and other activity is occurring in the pool, the
potential for a pool-full condition exists. In this case, Lifeguard may delete the
snapshot that you are restoring from.
The SWVR Lifeguard service is installed and automatically started. The
service checks each drive letter on a system to see if it is a virtual disk or a
snapshot. If it is a snapshot, Lifeguard checks the storage pool that the drive
belongs to for its amount of current free space. This check is performed, by
default, once every 10 seconds.
The TaskSmart N2400 appliance implementation of SWVR uses the following
default settings for the SWVR Lifeguard service:
Checks for pool-full situations once every 10 seconds
Begins deleting snapshots when the free pool space drops below the
1,024-MB threshold
CAUTION: If the pool is improperly sized and there is an insufficient amount of
free space in the pool, Lifeguard automatically deletes the oldest snapshots.
This action prevents a critical space deficit that could delay or lose writes.
CAUTION: The consequence of utilizing Lifeguard is that during a restore
Lifeguard can cause the loss of the original data represented in a snapshot. If
the amount of free space goes below a specific threshold, Lifeguard deletes one
or more snapshots to make more space available in the pool. See the
"Snapshots and Restoring a Virtual Disk" section for more information.
Administrative Procedures 2-29