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

To: "rudi@xxxxxxxxxxx" <rudi@xxxxxxxxxxx>
Subject: RE: [Xen-users] iscsi vs nfs for xen VMs
From: Matej Zary <matej.zary@xxxxxxxxx>
Date: Wed, 26 Jan 2011 10:27:19 +0100
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Thread-topic: [Xen-users] iscsi vs nfs for xen VMs
More on the bottom of message, Exchange and OWA sucks. :(
From: Rudi Ahlers [Rudi@xxxxxxxxxxx]
Sent: 26 January 2011 09:55
To: Matej Zary
Cc: jg@xxxxxxxxxxxx; Dustin Black; xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] iscsi vs nfs for xen VMs

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 ?

Kind Regards
Rudi Ahlers

Website: http://www.SoftDux.com
Technical Blog: http://Blog.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532

Well, that sucks. We are in similar situation storage vise, we have HP XP24000 
(made by Hitachi) with midrange IBM Dseries extending the capacity. And if the 
XP fails, we are screwed, even though we have all needed backups on tapes - we 
run VMware ESX  (not my choice :D) in this datacenter, but the HW resources 
(blade servers) doesn't offer enough local disk capacity to run the VMs locally 
in catastrophic scenario.

Solution can be "enterprise" NAS/SAN redundancy. Some of the enterprise storage 
devices can be onlince synced with another even in another distant geographical 
location (e.g NetApp, our XP offers something a bit similar IIRC). Sure it has 
performance hit, but whats worse, it cost shitload of money, so it's out of the 
question in most cases. :/

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