[Gluster-users] Why is it not possible to mount a replicated gluster volume with one Gluster server?

[Atin Mukherjee]

-Atin
Sent from one plus one
On Sep 1, 2015 9:39 PM, "Joe Julian" <joe at julianfamily.org> wrote:
>
>
>
> On 09/01/2015 02:59 AM, Atin Mukherjee wrote:
>>
>>
>> On 09/01/2015 02:34 PM, Joe Julian wrote:
>>>
>>>
>>> On 08/31/2015 09:03 PM, Atin Mukherjee wrote:
>>>>
>>>> On 09/01/2015 01:00 AM, Merlin Morgenstern wrote:
>>>>>
>>>>> this all makes sense and sounds a bit like a solr setup :-)
>>>>>
>>>>> I have now added the third node as a peer
>>>>> sudo gluster peer probe gs3
>>>>>
>>>>> That indeed allow me to mount the share manually on node2 even if
>>>>> node1 is
>>>>> down.
>>>>>
>>>>> BUT: It does not mount on reboot! It only successfully mounts if
>>>>> node1 is
>>>>> up. I need to do a manual: sudo mount -a
>>>>
>>>> You would need to ensure that at least two of the nodes are up in the
>>>> cluster in this case.
>>>
>>> Atin, why? I've never had that restriction.
>>>
>>> It sounds to me like the mount's trying to happen before any bricks are
>>> available and/or glusterd is listening.
>>
>> In a 3 node cluster if two of the nodes are already down and the other
>> is rebooted then the GlusterD instance wouldn't start the brick process
>> until it receives the first handshake from one of its peer and for that
>> you would need your 2nd node to be up as well. This why its recommended
>> to have a 3rd dummy node (without any bricks) added to a existing 2 node
>> cluster.
>
>
> Again I ask, is this a departure from prior behavior?
Not really, its there from long time. IIRC, this change was done when
quorum feature was introduced. KP can correct me.
>
>
>>>>> Is there a particular reason for this, or is it a misconfiguration?
>>>>>
>>>>>
>>>>>
>>>>> 2015-08-31 21:01 GMT+02:00 Joe Julian <joe at julianfamily.org>:
>>>>>
>>>>>> On 08/31/2015 10:41 AM, Vijay Bellur wrote:
>>>>>>
>>>>>>> On Monday 31 August 2015 10:42 PM, Atin Mukherjee wrote:
>>>>>>>
>>>>>>>>    > 2. Server2 dies. Server1 has to reboot.
>>>>>>>>    >
>>>>>>>>    > In this case the service stays down. It is inpossible to
>>>>>>>> remount the
>>>>>>>> share without Server1. This is not acceptable for a High
Availability
>>>>>>>> System and I believe also not intended, but a misconfiguration or
>>>>>>>> bug.
>>>>>>>> This is exactly what I gave as an example in the thread (please
read
>>>>>>>> again). GlusterD is not supposed to start brick process if its
other
>>>>>>>> counter part hasn't come up yet in a 2 node setup. The reason it
has
>>>>>>>> been designed in this way is to block GlusterD on operating on a
>>>>>>>> volume
>>>>>>>> which could be stale as the node was down and cluster was
operational
>>>>>>>> earlier.
>>>>>>>>
>>>>>>> For two node deployments, a third dummy node is recommended to
ensure
>>>>>>> that quorum is maintained when one of the nodes is down.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Vijay
>>>>>>>
>>>>>> Have the settings changed to enable server quorum by default?
>>>>>>
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>>>>>>
>>>>>
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>>>
>
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