[Users] GlusterFS Distributed Replicate

[Andrew Lau]

On Sat, Dec 21, 2013 at 4:43 AM, <gregoire.leroy at retenodus.net> wrote:

> Hi,
>
>   keepalived is only for grabbing the gluster volume info (eg. the servers
>> which host the bricks) > in which from what I've noticed your clients will
>> then connect to the gluster servers directly
>> (not using keepalived anymore).
>>
>
> Can't keepalived be replace by naming the hostname by localhost, as what
> Alex says ?

Yes it could sorry I forgot about that method, I used to do it that way but
we had plans on possibly implementing nodes without glusterfs bricks
possibly in the future so we moved to keepalived.

>
>
>  If you disable quorum then you won't have the issue of "read only" when
>> you lose a host, but you > won't have protection from split brain (if your
>> two hosts lose network connectivity). VMs will
>> keep writing to the hosts, as you have the gluster server and client on
>> the same host this is
>> inevitable.
>>
>
> Ok, I get the problem caused by disabling the quorum. So, what if while
> I've two hosts the lack of HA is not so dramatic but will be necessary when
> I'll have more hosts ? (3 or 4). Here is the scenario I would like to have :
>

Quorum generally requires 3 hosts, I believe the default configuration when
you press "Optimize for virt store" will require a minimum of 2 bricks
connected before writing is allowed.


> 1) I have two hosts : HOSTA and HOSTB. They have glusterfs bricks
> configured as Distribute Replicated and data is replicated.
> => For now, I'm totally ok with the fact that if a node fails, then VM on
> this hosts are stopped and unreachable. However, I would like that if a
> node fails, the DC keeps running so that VM on the other hosts are not
> stopped and a human intervention make possible to start the VM on the other
> host. Would it be possible without disabling the quorum ?
>

For the 2 host scenario, disable quorum will allow you to do this.

>
> 2) In few months, I'll add two other hosts to the glusterfs volum. Their
> bricks will be replicated.
> => At that time, I would like to be able to make evolve my architecture
> (without shut my VM and export/import them on a new cluster) so that if a
> node fails, VM on this host start to run on the other host of the same
> brick (without manual intervention).
>

Later on you just enable quorum, it's only a setting in the gluster volume.
gluster volume set DATA cluster.quorum-type auto

>
> Is it possible ?
>
> Le 2013-12-20 16:22, a.ludas at gmail.com a écrit :
>
>  Hi,
>>
>> in a 2 node cluster you can set the path to localhost:volume. If one
>> host goes down and SPM role switches to the remaining running host,
>> your master domain is still accessible and so your VMs stay up and
>> running.
>>
>> Regards,
>> Alex
>>
>
> I tried it but still, the storage/cluster were shutdown, probably because
> of the quorum.
>
>
> Thank you very much,
> Regards,
> Grégoire Leroy
>
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