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



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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