RE: [Xen-users] iscsi vs nfs for xen VMs

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> On Wed, Jan 26, 2011 at 10:44 AM, Matej Zary <matej.zary@xxxxxxxxx> wrote:
> > Depends on quality of NAS/SAN device. Some of them are more reliable&robust
> that rest of the infrastructure (dual controllers, raid6, multipathing etc.),
> obviously they cost arm&leg. So they SHOULD not totally fail (firmware issues
> are  another thing though). And in that case, even if one owns enterprise
> grade storage, backups (tape, another storage, remote site) are always must.
> Yeah, if storage fails, there will be downtime. You can still have locals
> disks on xen host. So for example you can restore most important Xen guests on
> the local disks from backups and live without live migration until the NAS/SAN
> issues are solved.
> >
> > Matej
> > ________________________________________
> 
> 
> Well, that's the problem. We have (had, soon to be returned) a so
> called "enterprise SAN" with dual everything, but it failed miserably
> during December and we ended up migrating everyone to a few older NAS
> devices just to get the client's websites up again (VPS hosting). So,
> just cause a SAN has dual PSU's, dual controllers, dual NIC's, dual
> HEAD's, etc doesn't mean it's non-redundant.
> 
> I'm thinking of setting up 2 independent SAN's, of for that matter
> even NAS clusters, and then doing something like RAID1 (mirror) on the
> client nodes with the iSCSI mounts. But, I don't know if it's feasible
> or worth the effort. Has anyone done something like this ?
> 

There are plenty of recipes for DRBD + pacemaker/heartbeat + iSCSI. With 
appropriate redundancy in place and plenty of testing you should be able to 
build something that's pretty much bulletproof.

James


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