Re: [Xen-users] Safe iSCSI & Live Migrations

[Simon Capstick <simon@xxxxxxxxxxxxxxxx>]

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no longer actively maintained.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/




_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users