[ovirt-users] [Ovirt 4.1] Hosted engine with glusterfs (2 node)

[TranceWorldLogic .]

Should I consider that there is no use of Quorum on 2 node.
I need to setup odd :)  nodes only.

Please clarify same.

Thanks,
~Rohit

On Tue, Jul 11, 2017 at 12:57 PM, Simone Tiraboschi <stirabos at redhat.com>
wrote:

>
>
> On Tue, Jul 11, 2017 at 7:17 AM, TranceWorldLogic . <
> tranceworldlogic at gmail.com> wrote:
>
>> Hi,
>>
>> I was trying to setup hosted engine on 2 host machine but it not allowing
>> to setup hosted engine on 2 node gluster file system.
>>
>> I have also modified vdsm.com to allow 2 replica count.
>>
>> But latter I found in code it is hard coded to 3 as shown below:
>> ------------------- -------------------------------
>> ------------------------------ ---------------
>> src/plugins/gr-he-setup/storage/nfs.py
>>
>>         if* replicaCount != '3'*:
>>             raise RuntimeError(
>>                 _(
>>                     'GlusterFS Volume is not using replica 3'
>>                 )
>>             )
>> ------------------- -------------------------------
>> ------------------------------ ---------------
>>
>> Can I get to know the reason to hard coded to 3 ?
>> from online I got to know that split brain issue not get resolve
>> automatically using 2 node gluster setup. But please let me know more (why
>> 3 ? why not 2 or 4 ?)
>>
>
> Simply because two is even and three is odd.
>
> In a split condition over only two nodes, if node A says A and nodes B
> says B you cannot decide if the truth is A or B.
> With three nodes, if node says A but nodes B AND nodes C says B, the truth
> is B by design.
> That's why you need three nodes with at least 2 of them up and working.
>
> If you want to save something on storage side you could evaluate two
> regular nodes plus an arbiter one.
>
>
>>
>> If I am missing something please let me know.
>> Also want to understand, can quorum can solve 2 node gluster issue
>> (split-brain) ?
>>
>> Thanks,
>> ~Rohit
>>
>>
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>>
>>
>
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