Re: [Xen-users] xen storage options - plase advise

[Thomas Halinka <lists@xxxxxxxxx>]

Hi James,

Am Mittwoch, den 03.03.2010, 17:34 -0500 schrieb James Pifer:
> > Are your file backed domUs are on a SAN/NAS? If not, where do the disks
> > that make up your cluster reside? You can cluster LVM, though you loose
> > snapshotting, and NFS is also worth considering depending on how the 
> > shares are exported e.g. via a NAS where hardware can be more easily
> > hot-swapped. Migration to NFS would be easy as well since you could just
> > mount your files, copy the contents to an NFS share, and restart your domU.
> > 
> > Jamon
> 
> 
> Yes, file based domU's are currently on ocfs2 on a SAN. 
> 
> I don't do any snapshotting right now, but that's not to say I won't
> want to some day.

Yes, but you _want_ to be able snapshot your domUs, because of
"Hot-backup" of running domUs.

>  My goal is to get to a point where things are stable
> and I can run something to manager everything, ie Orchestrate,
> Convirture, something to manage restarting/migrating domU's when one of
> the servers has problems. Or I just need to have a server down for
> maintenance.

You're searching for openQRM ;-)

> So in general terms, how would I setup LVM (clvm)? Let's say I have two
> servers (in this case running sles11). Each server has the SAME
> vdisk(LUN) from our Xiotech SAN assigned to it for storage. Let's say
> it's a 400gb vdisk. If I add additional servers, they too would be
> assigned the same vdisk. Similarly, I could add additional vdisks when
> more storage is required. 

You have to care that _EVERY_ dom0 is "seeing" the Storage-LUN!

If your hosts are able to connect to this storage ALL Hosts should be
able to use this Volumes (LVols)

> 
> Anyway, on the first server I setup LVM. Somehow the second server would
> also see that as lvm and be able to mount it?

pvscan 
vgscan 
vgchange -ay 

should be enough that ALL Hosts could start the domUs residing in this
LUN / VG....

Just put something like this in a init-script....

> I will search for some documentation on setting up clvm, but my
> questions are:
> 
> 1) Is this where I would/could use clvm? 

yes, but if you use a Management-Tool like openQRM, ConVirt or whatever
the Management-Solution takes care of starting/stopping DomUs, so
Locking is not really necessary..

> 2) On each server would they see the logical volume at a mount point?

yes

> 3) Would I need to use xen's built in locking mechanisms or is there
> some builtin locking like ocfs2 has?

Nope. You have just to take care, that you dont start your DomUs twice.
So just use a Management-Solution, which takes care of this.

> The only way I'm familiar with nfs is by running nfs on a server and
> then other servers mounting nfs from that server. Are you saying that
> the SAN could somehow directly provide nfs? 

e.g. NXXAPP provide direct NFS-Access, ZFS-based-Solution like
NexentaStore, too... and so on

It depends of the Vendor, which storage-technologies are supported and
available...

> Sorry if some of my questions don't make sense.
> Thanks,
> James


hth,


thomas
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