libvirt users - Feb 2011 - iSCSI storage pool questions

Hi All,
I've been trying to figure out the best way of using an iSCSI SAN with KVM
and thanks to a helpful post by Tom Georgoulias that I found on this list
(https://www.redhat.com/archives/libvirt-users/2010-May/msg00008.html), it
appears I have a solution.

What I'm wondering is the following:

1) If I use an iSCSI LUN as the storage pool (instead of creating an LVM VG from
this iSCSI LUN manually first and using LVM in libvirt) do I loose any
functionality (such as snapshotting)?

2) If I am intending on doing offline & live-migration between hosts, does
each host have to connect to the same LUN / storage pool, or should each host
have a separate LUN that is stores VMs on and then each host should simply see
all of the LUNs so that migration is possible?

For example:
I create a LUN on the SAN, connect this to host 1 as a pool called "pool
1" and create VMs on it.
Then, on host 2, do I connect to the same "pool 1" and create VMs
there, or do I just connect to "pool 1" in order to see it (for
migrations) but also define "pool 2" from another new LUN on the SAN
and create VMs there? Hope that makes sense..

I'm trying to understand in what situations I might get myself in trouble by
two hosts performing storage operations at the same time on the same pool (which
is unlikely, but I'm trying to figure out where I stand)


Thanks!
Anthony
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I think I may have inadvertently answered one of my questions, I was under the
impression that an iSCSI storage pool was simply a pool of disk that libvirt
could then create individual disks on (similar to an LVM VolumeGroup and Logical
Volumes). But it seems that all disk creation has to happen on the SAN side when
setup this way.

Is anyone aware of good guides for setting up a similar scenario using iSCSI
backed LVM? I'm worried about consistency & corruption across hosts and
I'd love to see an example of a working setup documented somewhere.

Cheers,
Anthony


On Feb 2, 2011, at 4:26 PM, Anthony Goddard wrote:
> Hi All,
> I've been trying to figure out the best way of using an iSCSI SAN with
KVM and thanks to a helpful post by Tom Georgoulias that I found on this list
(https://www.redhat.com/archives/libvirt-users/2010-May/msg00008.html), it
appears I have a solution.
> 
> What I'm wondering is the following:
> 
> 1) If I use an iSCSI LUN as the storage pool (instead of creating an LVM VG
from this iSCSI LUN manually first and using LVM in libvirt) do I loose any
functionality (such as snapshotting)?
> 
> 2) If I am intending on doing offline & live-migration between hosts,
does each host have to connect to the same LUN / storage pool, or should each
host have a separate LUN that is stores VMs on and then each host should simply
see all of the LUNs so that migration is possible?
> 
> For example:
> I create a LUN on the SAN, connect this to host 1 as a pool called
"pool 1" and create VMs on it.
> Then, on host 2, do I connect to the same "pool 1" and create VMs
there, or do I just connect to "pool 1" in order to see it (for
migrations) but also define "pool 2" from another new LUN on the SAN
and create VMs there? Hope that makes sense..
> 
> I'm trying to understand in what situations I might get myself in
trouble by two hosts performing storage operations at the same time on the same
pool (which is unlikely, but I'm trying to figure out where I stand)
> 
> 
> Thanks!
> Anthony
> _______________________________________________
> libvirt-users mailing list
> libvirt-users at redhat.com
> https://www.redhat.com/mailman/listinfo/libvirt-users
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