Hi,

There are some things I don't understand. First of all, why do we need keepalived ? I thought that it would be transparent at this layer and that glusterfs would manage all the replication thing by itself. Is that because I've POSIXFS instead of GlusterFS or is it totally unrelated ?

Secondly, about the split-brain, when you says that I can read but not write, does that mean I can't write data on the VM storage space or can't I create VM ? If I can't write data, what would be the workaround ? Am I force to have 3 (or 4, I guess, as I want to get replication) nodes ?

To conclude : can I get real HA (except engine) with Ovirt / Glusterfs with 2 nodes ?

Thank you very much,
Regards,
Grégoire Leroy


Le 2013-12-19 23:03, Andrew Lau a écrit :

Hi,

 What I learned in the way glusterfs works is you specify the host
only to grab the initial volume information, then it'll go directly to
the other hosts to connect to the datastore - this avoids the
bottleneck issue that NFS has.

Knowing this, the work around I used was to setup keepalived on the
gluster hosts (make sure you set it up on an interface other than your
ovirtmgmt or you'll clash with the live migration components). So now
if one of my hosts drop from the cluster, the storage access is not
lost. I haven't fully tested the whole infrastructure yet but my only
fear is they may drop into "PAUSE" mode during the keepalived
transition period.

Also - you may need to change your glusterfs ports so they don't
interfere with vdsm. My post here was a little outdated but it still
has my findings on keepalived
etc. http://www.andrewklau.com/returning-to-glusterized-ovirt-3-3/

[2]

The other thing to note, is you've only got two gluster hosts. I
believe by default now ovirt sets the quorum setting which enforces
that there must be atleast 2 nodes alive in your configuration. This
means when there is only 1 gluster server up, you'll be able to read
but not write this is to avoid split-brain.

Thanks,
Andrew

On Thu, Dec 19, 2013 at 5:12 AM, <gregoire.leroy@retenodus.net> wrote:

Hello,

As I said in a previous email, I have this configuration with Ovirt
3.3 :
1 Ovirt Engine
2 Hosts Centos 6.5

I successfully setup GlusterFS. I created a distributed replicate
volume with 2 bricks : host1:/gluster and host2:/gluster.

Then, I created a storage storage_gluster POSIXFS with the option
glusterfs and I gave the path "host1:/gluster".

First, I'm rather surprised I have to specify an host for the
storage as I wish to have a distribute replicated storage. I
expected to specify both hosts.

Then I create a VM on this storage. The expected behaviour if I
shutdown host1 should be that my VM keeps running on the second
brick. Yet, not only I lose my VM but host2 is in a non operationnal
status because one of its data storage is not reachable.

Did I miss something in the configuration ? How could I get the
wanted behaviour ?

Thanks a lot,
Regards,
Grégoire Leroy
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[1] http://lists.ovirt.org/mailman/listinfo/users
[2] http://www.andrewklau.com/returning-to-glusterized-ovirt-3-3/