[ovirt-users] Change gluster primary

[John Gardeniers]

Hi Alex,

I understand what you're saying and certainly there is no primary from 
the Gluster perspective. However, things are quite different as far as 
Ovirt/RHEV is concerned.

We had an incident last week where we had to take nix off-line. A 
network glitch then caused a our RHEV to briefly lose connection to 
jupiter. This resulted in all VMs crashing because the system was trying 
to reconnect to nix. It did not try to reconnect to jupiter, despite it 
being configured as the fail-over server. In the end I had to bring nix 
back on line. RHEV still wouldn't connect. Finally, I had to reboot each 
hypervisor. Even then, two of them still failed to reconnect and could 
only be brought back by performing a full reinstall (we're using the 
cut-down dedicated RH hypervisors, not the RHEL+hypervisor that you 
use). All in all, quite a disastrous situation that lost us a couple of 
hours. So yes, there is a primary from the Ovirt/RHEV perspective and 
I'm really disappointed in how the system completely failed to handled 
the situation.

regards,
John


On 21/01/15 00:20, Alex Crow wrote:
> Hi John,
>
> There isn't really a primary in gluster. If you're using a glusterfs 
> storage domain, you could turn off "nix" and the VMs would continue to 
> run (although you'd have to disable quorum if you currently have it 
> enabled on the volume, and you'd have to repoint the domain at some 
> later point). If you're using NFS access you would have to repoint 
> your storage to the remaining machine immediately.
>
> The only snag I can see is that you can't detach the master storage 
> domain in Ovirt if any VMs are running. I think you'd have to shut the 
> VMs down, put the storage domain into maintenance, and then edit it.
>
> Cheers
>
> Alex
>
> On 19/01/15 23:44, John Gardeniers wrote:
>> We are using Gluster as our storage backend. Gluster is configured as 
>> 2 node replica. The two nodes are name nix and jupiter. At the Ovirt 
>> (RHEV really) end we have the gluster path configured as 
>> "nix:/gluster-rhev", with a mount option of 
>> "backupvolfile-server=jupiter.om.net". We now need to replace nix 
>> with a new server, which cannot have the same name. That new server 
>> will be the primary, with jupiter remaining the secondary.
>>
>> We will have all VMs and hypervisors shut down when we make this change.
>>
>> What is the best and/or easiest way to do this? Should we just 
>> disconnect the storage and re-attach it using the new gluster 
>> primary? If we do that will our VMs just work or do we need to take 
>> other steps?
>>
>> An alternative, which I suspect will be somewhat controversial, would 
>> be to make a direct edit of the engine database. Would that work any 
>> better or does that add more dangers (assuming the edit is done 
>> correctly)?
>>
>> regards,
>> John
>>
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>