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

Yannis Milios yannis.milios at gmail.com
Sat Aug 26 13:56:45 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.


Have you considered a HA NFS over a 2-node DRBD8 cluster ? Should work well
on most hypervisors (qcow2,raw,vmdk based).

Yannis

On 26 Aug 2017 12:16, "A.Rubio" <aurusa at etsii.upv.es> wrote:

> Hi all.
>
> I writted a book about this every years ago for a course.
>
> The book is about pacemaker, drbd, gfs2 and kvm, for 2 nodes and for many
> nodes.
>
> It's writted in spanish because my english is poor (it's evident :-()
>
> http://www.lulu.com/shop/aurelio-rubio-sapi%C3%B1a-and-juan-
> vicente-capella-hern%C3%A1ndez/pacemaker-clusters-de-alta-
> disponibilidad-para-servidores-virtualizados/ebook/product-22274638.html
>
> If yo want a copy and you can't buy it ;-), You write to my. I don't have
> problem send you the ebook.
>
>
> El 25/08/2017 a las 22:18, Digimer escribió:
>
>> 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).
>>
>> https://www.alteeve.com/w/The_2-Node_Myth
>>
>> 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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