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xen-users
Re: [Xen-users] Safe iSCSI & Live Migrations
James Harper wrote:
I'm currently playing with iSCSI and Xen (exporting individual DomU
block devices as individual iSCSI disks) and wanted to find a safe way
to use iSCSI. i.e. I want to prevent the accidental mounting of an
iSCSI
disk from two or more machines. Using IET as an iSCSI target I can
set
MaxConnections=1 in the config. This ensures that no accidental
filesystem corruption happens due to two or more simultaneous mounts.
However live migration is out of the question. To move a DomU from
one
box to another with the MaxConnections=1 safeguard I have to;
Box 1:
Shutdown the DomU.
Perform an iSCSI logout.
Box 2:
Perform an iSCSI login.
Start the DomU.
Is there any way to perform a live migration of the above by getting
Xen
to run iSCSI logout/login scripts as the DomU pauses in the middle of
the live migration? Are there any software hooks that can be used to
do
this?
Or are there simpler methods to guarantee the safe/single use of iSCSI
disks that still allow Xen's live migration?
It sounds like Dom0 is making the iSCSI connection and exporting the
block device to DomU... is that the case?
If DomU initiated the iSCSI connection then I think this would solve all
of your problems, although it would create some of its own - root on
iSCSI can be a bit tricky.
James
You're quite correct, Dom0 is exporting block devices to the DomUs. I
was trying to keep iSCSI out of the DomU's, but maybe in the end that is
the easiest way to achieve safe iSCSI with Live Migrations.
A description of what may be involved with booting off iSCSI directly
from within a DomU can be found here [1]. It looks like the author had
to hard code the iSCSI configuration in the custom initrd.img, and
change it for each DomU.
The iscsi-init project [2] looks more promising, but it looks like it is
no longer actively maintained.
Simon
[1] http://www.eludicate.com/~bolen/iscsi/#4.1_Overview
[2] http://iscsi-init.sourceforge.net/
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