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Copyright@2004~2014 Qsan Technology, Inc. All Rights Reserved.
Qsan Document – User Manual
Change Controller Mode
The operation mode can be changed from Single to Dual or vice versa. Please follow the
procedures to change the operation mode.
1.
In
System Maintenance -> Upgrade
tab, select
Single
or
Dual
in the drop-down list.
2.
Click
Apply
button, it will pop up a warning message, click
OK
button to confirm.
Recommend iSNS Server
In addition, iSNS server is recommended. It’s important for keeping I/O running smoothly when
the ownership of the RAID group is switching or one of the dual controllers fails. For example of
without iSNS server, when the controller 1 fails, the running I/O from host to controller 1 may fail
because the host switches to new portal is slower at the moment and it may cause I/O time out.
With iSNS server, this case would not happen.
TIP:
iSNS server is recommended for dual controller system of iSCSI interfaces.
Snapshots
Snapshot-on-the-box captures the instant state of data in the target volume in a logical sense. The
underlying logic is Copy-on-Write, moving out the data which would be written to certain location
where a write action occurs since the time of data capture. The certain location, named as
“Snapshot virtual disk”, is essentially a new virtual disk which can be attached to a LUN
provisioned to a host as a disk like other ordinary virtual disks in the system.
Rollback restores the data back to the state of any time which was previously captured in case for
any unfortunate reason it might be (e.g. virus attack, data corruption, human errors and so on).
Snapshot virtual disk is allocated within the same RAID group in which the snapshot is taken, we
suggest to reserve 20% of the RAID group size or more for snapshot space. Please refer to the
following figure for snapshot concept.
