[DRBD-user] DRBD Dual Primary + GFS2 for redundant KVM hosts

Digimer lists at alteeve.ca
Fri Aug 25 22:18:14 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On 2017-08-25 04:08 PM, Gionatan Danti wrote:
> Il 25-08-2017 22:01 Digimer ha scritto:
>> On 2017-08-25 03:37 PM, Gionatan Danti wrote:
>> The overhead of clustered locking is likely such that your VM
>> performance would not be good, I think.
> Mmm... I need to do some more testing with fio, it seems ;)
>> With raw clustered LVs backing the servers, you don't need cluster
>> locking on a per-IO basis, only on LV create/change/delete. Because LVM
>> is sitting on top of DRBD (in dual-primary), live-migration is no
>> trouble at all and performance is good, too.
> True.
>> GFS2, being a cluster FS, will work fine if a node is lost, provided it
>> is fenced succesfully. It's wouldn't be much of a cluster-FS
>> otherwise. :)
> So no problem with quorum? A loss of a system in a two-node cluster
> seems to wreack havok on other cluster filesystems (Gluster, for
> example...)
> Thanks.

Quorum is optional (an often misunderstood thing).


We've run without quorum for every system we've built over 5+ years,
across dozens of sites and never once needed it. A proper fence setup,
which is needed regardless, is fine. In our opinion, the complexity of a
third quorum node is not justified for the limited benefit of quorum.
Simplicity is simply too valuable in HA.

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