User's Manual

39
Using snapshot with Open-E iSCSI
Usage snapshot facility heavily depends on the initiator of software support for
dynamic units* and the partition scheme which you use on the operating system
where you attach the targets. The most common error is if on the client side that
uses an LVM/LVM2 (Linux) scheme or Microsoft's Dynamic Disks which connect
to the snapshot and original volume from the same client malfunctions. This is
due to the fact that normally an LVM volume bares special metadata which is
used as the identify information and since a snapshot simply doubles those
metadata it can confuse your partitioning software (for example logical volume
manager sees two identical volumes).
In order to take proper advantage of Open-E iSCSI Target's snapshot technology
the volumes your Open-E iSCSI Target exports should be imported in your
operating system as Basic Volume (Windows) and you should not incorporate
them as logical volumes in LVM/LVM2 (on Linux) if you plan to use snapshots
and access them from the same machine at the same time.
If you plan to take snapshots and import them alongside the original volume -
access them from the same client. Below is instruction how to import a target in a
Microsoft basic volume:
a. Create target volumes (tgv),
b. Create a target in Open-E iSCSI,
c. Add chosen volumes to the target.
d. In MS iSCSI Initiator add Open-E iSCSI Target as an iSCSI portal in the MS iSCSI
Initiator console,
e. Log onto the target,
f. Open the computer management,
i.
reserve
reserved space as needed. To activate a snapshot go Maintenance
j.
ntly iSCSI Microsoft Initiator ver1.06 does not support dynamic volumes.
g. Select the disk management,
h. Add the volumes as basic disks,
On Open-E iSCSI Target create snapshots: setup Æ target manager and
desired space for snapshots (reserve about 5-20% of total space for the
snapshots). Determine number of snapshots, assigned to the volumes and
distribute the
Æ Snapshot.
Follow the steps e-h to log and attach the snapshot target.
*) Curre
et
apshots, (RAID previously
d.
The best solution to use snapshots without decreasing Open-E iSCSI
performance is to assign separate RAID. This RAID will be optimized for
a writing speed (e.g. few disks in RAID 0 only for snapshots). Follow the
steps below:
a. Add RAID chosen for data as NEW (Vg0) in the menu WebGui: setup Æ targ
manager Æ Volumes,
b. Create one or more Tgv’s. At this point, there is no free space reserved for
snapshots,
c. Add the second RAID to existing Vg0, intended for sn
configured as RAID 0),
Now only reserve all available space for snapshots.