Qsan Technology P300H61, User Manual

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The QReplica uses QSnap , the snapshot technique of QSAN , to help user to replicate
the data without stop accessing to the source virtual disk. If the snapshot space is not
configured on the source virtual disk in advance, the subsystem will allocate snapshot
space for the source virtual disk automatically when the replication job is created. The
default snapshot space allocated by the subsystem is two times the size of source virtual
disk. If the free space of the RAID group which the source virtual disk resides in is less
than double size of the source virtual disk, the replication job will fail and pops up the
error message.
To prevent this problem, user has to make sure the RAID group has enough free space for
the snapshot space of source virtual disk, or user has to configure the snapshot space of
the source virtual disk manually before the replication job is created.
1.
To configure the snapshot space settings of QReplica, click the “configuration”
button.
Figure 5.11.21
There are three settings in the
QReplica configuration menu,
Figure 5.11.22
“Snapshot space” specifies the ratio of snapshot space allocated to the source virtual
disk automatically when the snapshot space is not configured in advance. The default ratio
is 2 to 1. It means when the replication job is creating, the subsystem will automatically
use the free space of RAID group to create a snapshot space which size is double of the
source virtual disk.
“Threshold” setting will monitor the utilization of snapshot space. When the used
snapshot space achieves the threshold, the subsystem will automatically take a new
snapshot and start the replication job. The purpose of threshold is to prevent the
incremental copy fail immediately when running out of snapshot space. For example, the
default threshold is 50%, and the system will check the snapshot space every hour. When
the snapshot space is used over 50%, the subsystem will automatically replicate data from