[DRBD-user] DRBD over ZFS - or the other way around?

Gionatan Danti g.danti at assyoma.it
Fri Aug 18 21:26:22 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
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Il 18-08-2017 17:09 Yannis Milios ha scritto:
> Personally I'm using option (a) on a 3 node proxmox cluster and drbd9.
> Replica count per VM is 2 and all 3 nodes act as both drbd control
> volumes and satellite nodes.I can live migrate VM between all nodes
> and snapshot them by using drbdmanage utility (which is using zfs
> snapshot+clones).

Hi Yannis, thank you for describing your setup!

> Option (b) seems more suitable for a 2 node drbd8 cluster in a
> primary/secondary setup. Haven't tried it so I cannot tell if there
> are any clurpits. My only concern in such setup would be if drbd
> corrupts silently the data on the lower level and zfs is not aware of
> that.

I think that such a silent corruption will be better caught by ZFS when 
it happens at the lower layer (ie: the ZOOL, at VDEV level) rather than 
when it happens at upper layers (ie: DRBD on ZVOL). This is the stronger 
argument why on the ZFS list I was adviced to use DRBD on RAW device + 
ZFS on higher layer.

 From what I read on this list, however, basically no-one is using ZFS 
over DRBD over RAW disks, so I am somewhat worried about some potential, 
hidden pitfalls.

> Also, if you are *not* going to use live migration, and you can
> afford loosing some seconds of data on the secondary node in favor of
> better performance on the primary node, then you could consider using
> protocol A instead of C for the replication link.

Sure. On other installation, I am using protocol B with great success.

Thanks.

-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti at assyoma.it - info at assyoma.it
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