Re: [Xen-users] Re: Xen + SAN

[Matthew Wild <Matthew.Wild@xxxxxxxxxx>]

On 23/06/11 22:04, Shaun Reitan wrote:
> > iSCSI and AOE export the storage as raw block devices to the
> > hypervisors - which basically act the same as local storate (i.e. SATA
> > / SAS HDD's in the server) so you then either need to partition the
> > iSCSI LUN the same way as you do with local drives, or the easier way
> > is to use LVM to "slice" it up and then use LVM volumes for the domU
> > virtual machines
>
> I don't know about AOE but with ISCSI the problem I'm seeing is that if
> i create a volume group on the SAN there is no way to export that volume
> group. I could export the device that the volume group was created on
> but then the host doesn't see that VG. I'm assuming i would need to use
> clustered LVM for that which i have been told to stay far away from.
> Another option was to carve out the LV's on the SAN and to export each
> LV to the initiators but still the problem is that the host assigns
> these luns to /dev/sd devices and there's no simple nice way to map them
> to who owns what disk. Least not that I've found yet. I'm fairly new to
> ISCSI though so maybe there's something I'm missing.
>
> ~Shaun
Hi Shaun,
	I've not kept up with what Linux distro. you're using, but the various 
udev rules tend to give persistent naming of devices under the 
/dev/disk/by-<id|path|uuid> directories.
For example, in /dev/disk/by-path on one of my Xen dom0's I can see

ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.hinode-ops-lun-0
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.hinode-ops-lun-0-part1
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.hinode-ops-lun-0-part2
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.stereo-ext-lun-0
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.stereo-ext-lun-1
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.ukssdc-helpdesk-lun-0
ip-10.0.0.1:3260-iscsi-iqn.2005-09.uk.ac:storage.ukssdc-helpdesk-lun-1

I then use these paths in the vm config file. This is then independent 
of the order I login to the iscsi devices.
Matthew
--
Matthew Wild                       Tel.: +44 (0)1235 445173
Matthew.Wild@xxxxxxxxxx                    URL http://www.ukssdc.ac.uk/
UK Solar System Data Centre and
World Data Centre - Solar-Terrestrial Physics, Chilton
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX

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