[ovirt-users] moving storage away from a single point of failure

[Alastair Neil]

My own experience with gluster for VMs is that it is just fine until you
need to bring down a node and need the VM's to be live.  I have a replica 3
gluster server and, while the VMs are fine while the node is down, when it
is brought back up, gluster attempts to heal the files on the downed node
and the ensuing i/o freezes the VM's until the heal is complete, and with
many VM's on a storage volume that can take hours.  I have migrated all my
critical VMs back onto NFS.   There are changes coming soon in gluster that
will hopefully mitigate this (better granualarity in the data heals, i/o
throttling during heals etc.)  but for now I am keeping most of my VMs on
nfs.

The alternative is to set the quorum so that the VM volume goes read only
when a node goes down.  This may seem mad, but at least your VMs are frozen
only while a node is down and not for hours afterwards.



On 22 September 2015 at 05:32, Daniel Helgenberger <
daniel.helgenberger at m-box.de> wrote:

>
>
> On 18.09.2015 23:04, Robert Story wrote:
> > Hi,
>
> Hello Robert,
>
> >
> > I'm running oVirt 3.5 in our lab, and currently I'm using NFS to a single
> > server. I'd like to move away from having a single point of failure.
>
> In this case have a look at iSCSI or FC storage. If you have redundant
> contollers and switches
> the setup should be reliable enough?
>
> > Watching the mailing list, all the issues with gluster getting out of
> sync
> > and replica issues has me nervous about gluster, plus I just have 2
> > machines with lots of drive bays for storage.
>
> Still, I would stick to gluster if you want a replicated storage:
>  - It is supported out of the box and you get active support from lots of
> users here
>  - Replica3 will solve most out of sync cases
>  - I dare say other replicated storage backends do suffer from the same
> issues, this is by design.
>
> Two things you should keep in mind when running gluster in production:
>  - Do not run compute and storage on the same hosts
>  - Do not (yet) use Gluster as storage for Hosted Engine
>
> > I've been reading about GFS2
> > and DRBD, and wanted opinions on if either is a good/bad idea, or to see
> if
> > there are other alternatives.
> >
> > My oVirt setup is currently 5 nodes and about 25 VMs, might double in
> size
> > eventually, but probably won't get much bigger than that.
>
> In the end, it is quite easy to migrate storage domains. If you are
> satisfied with your lab
> setup, put it in production and add storage later and move the disks.
> Afterwards, remove old
> storage domains.
>
> My to cent with gluster: It runs quite stable since some time now if you
> do not touch it.
> I never had issues when adding bricks, though removing and replacing them
> can be very tricky.
>
> HTH,
>
> >
> >
> > Thanks,
> >
> > Robert
> >
>
> --
> Daniel Helgenberger
> m box bewegtbild GmbH
>
> P: +49/30/2408781-22
> F: +49/30/2408781-10
>
> ACKERSTR. 19
> D-10115 BERLIN
>
>
> www.m-box.de  www.monkeymen.tv
>
> Geschäftsführer: Martin Retschitzegger / Michaela Göllner
> Handeslregister: Amtsgericht Charlottenburg / HRB 112767
> _______________________________________________
> Users mailing list
> Users at ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ovirt.org/pipermail/users/attachments/20150922/1b629842/attachment-0001.html>