[ovirt-users] 4-node oVirt with replica-3 gluster

[Sahina Bose]

On Fri, Sep 23, 2016 at 7:09 PM, Davide Ferrari <davide at billymob.com> wrote:

>
>
> 2016-09-23 13:50 GMT+02:00 Sahina Bose <sabose at redhat.com>:
>
> Ok, if I encounter again similiar problems I will post logs here
>
>
>>
>> If you have additional capacity on the other 3 hosts , then yes, you can
>> create a new gluster volume with a brick on the newly added 4th node and
>> bricks from other nodes - this volume can be used as another storage
>> domain. You are not doing anything wrong :) Keep in mind that all gluster
>> volumes used as data storage domains should be replica 3 or replica 3
>> -arbiter to avoid split-brain and data loss issues.
>>
>>
> Mmmmh this is ringing an alarm bell then. So, it's basically impossible
> (or at least not supported) a 4 hosts configuration with all the 4 hosts
> having a data domain in a replica 2 fashion? Is it only replica 3 arbiter 1
> the supported HA configuration? So if I want to expand storage (a part from
> adding disks to the same machines) I must add machines 3 by 3 ?
>
> Currently I have 4 machines with 4 disks each in a RAID-10 configuration,
> exposed as one brick. Which is the best HA solution in this scenario then?
>

You could do this - where Node3 & Node 2 also has arbiter bricks. Arbiter
bricks only store metadata and requires very low storage capacity compared
to the data bricks.

Node1  Node2     Node3        Node4
brick1   brick1      arb-brick
            arb-brick  brick1        brick1



> Thanks
>
> --
> Davide Ferrari
> Senior Systems Engineer
>
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