[Gluster-users] Replica 2 Quorum and arbiter

[Mahdi Adnan]

Thank you very much.

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Respectfully
Mahdi A. Mahdi

________________________________
From: Karthik Subrahmanya <ksubrahm at redhat.com>
Sent: Wednesday, April 19, 2017 4:30:30 PM
To: Mahdi Adnan
Cc: gluster-users at gluster.org
Subject: Re: [Gluster-users] Replica 2 Quorum and arbiter

Hi,
Comments inline.

On Tue, Apr 18, 2017 at 1:11 AM, Mahdi Adnan <mahdi.adnan at outlook.com<mailto:mahdi.adnan at outlook.com>> wrote:

Hi,


We have a replica 2 volume and we have issue with setting proper quorum.

The volumes used as datastore for vmware/ovirt, the current settings for the quorum are:

cluster.quorum-type: auto
cluster.server-quorum-type: server
cluster.server-quorum-ratio: 51%


Losing the first node which hosting the first bricks will take the storage domain in ovirt offline but in the FUSE mount point works fine "read/write"

This is not possible. When the client quorum is set to auto and the replica count is 2, the first node should be up for read/write to happen from mount. May be you are missing something here.

Losing the second node or any other node that hosts only the second bricks of the replication will not affect ovirt storage domain i.e 2nd or 4th ndoes.

Since the server-quorum-ratio is set to 51%, this is also not possible.
Can you share the volume info here?

As i understand, losing the first brick in replica 2 volumes will render the volume to read only

Yes you are correct, loosing the first brick will make the volume read-only.

, but how FUSE mount works in read write ?

Also, can we add an arbiter node to the current replica 2 volume without losing data ? if yes, does the re-balance bug "Bug 1440635" affect this process ?
Yes you can add an arbiter brick without losing data and the bug 1440635 will not affect that, since only the metadata need to be replicated on the arbiter brick.
And what happen if we set "cluster.quorum-type: none" and the first node goes offline ?
If you set the quorum-type to auto in a replica 2 volume, you will be able to read/write even when only one brick is up.
For an arbiter volume, quorum-type is auto by default and it is the recommended setting.

HTH,
Karthik

Thank you.

--

Respectfully
Mahdi A. Mahdi


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