[Gluster-users] GlusterFS as virtual machine storage

[lemonnierk at ulrar.net]

On Mon, Aug 21, 2017 at 10:09:20PM +0200, Gionatan Danti wrote:
> Hi all,
> I would like to ask if, and with how much success, you are using 
> GlusterFS for virtual machine storage.

Hi, we have similar clusters.

> 
> My plan: I want to setup a 2-node cluster, where VM runs on the nodes 
> themselves and can be live-migrated on demand.
> 

Use 3 nodes for gluster, or at the very least 2 + 1 arbiter. You really
really don't want a 2 node setup, you'll get split brains.

> I have some questions:
> - do you use GlusterFS for similar setup?

Yes, but always 3 nodes.

> - if so, how do you feel about it?

Works pretty well now, we've had problems but 3.7.15 works great. We are
currently testing 3.8, seems to work fine too. I imagine the newer ones
do aswell.

> - if a node crashes/reboots, how the system re-syncs? Will the VM files 
> be fully resynchronized, or the live node keeps some sort of write 
> bitmap to resynchronize changed/written chunks only? (note: I know about 
> sharding, but I would like to avoid it);

You really should use sharding, not sure exactly what happens without it
but I know it made the VM unusable during heal (they froze), basically.
Sharding solved that, with it it works well even during heal. It only
retransfert each shard so the amount to re-sync is pretty low.

> - finally, how much stable is the system?
> 

Haven't had any problems with gluster itself since we updated to >
3.7.11. It just works, even on a pretty bad network.
Performances aren't amazing, but I imagine you know that, replication
has a cost.

> Thanks.
> 
> -- 
> Danti Gionatan
> Supporto Tecnico
> Assyoma S.r.l. - www.assyoma.it
> email: g.danti at assyoma.it - info at assyoma.it
> GPG public key ID: FF5F32A8
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