Hi Joao,
Thanks for this valuable information. Ok another problem, I want to remove the mon host from the cluster here is my mon dump output
root@vms2:~# ceph mon dump
dumped monmap epoch 1
epoch 1
fsid 6ce085b5-1747-46f6-9fda-a3f1e8c75beb
last_changed 0.000000
created 0.000000
0: 192.168.1.128:6789/0 mon.vms1
1: 192.168.1.129:6789/0 mon.vms2
I tried to remove the the mon.vms2 from the cluster following this document http://ceph.com/docs/master/rados/operations/add-or-rm-mons/
but again its not worked.
root@vms2:~# service ceph -a stop mon.vms2
/etc/init.d/ceph: mon.vms2 not found (/etc/ceph/ceph.conf defines , /var/lib/ceph defines )
root@vms2:/etc/ceph# ceph mon remove mon.vms2
mon mon.vms2 does not exist or has already been removed
Br.
Umar
On Tue, Dec 17, 2013 at 6:18 PM, Karan Singh <ksingh@xxxxxx> wrote:
Thanks Joao for information.
Many Thanks
Karan Singh
----- Original Message -----
From: "Joao Eduardo Luis" <joao.luis@xxxxxxxxxxx>
To: ceph-users@xxxxxxxxxxxxxx
Sent: Tuesday, 17 December, 2013 2:56:23 PM
Subject: Re: After reboot nothing worked
On 12/17/2013 09:54 AM, Karan Singh wrote:
> Umar
>
> *Ceph is stable for production* , there are a large number of ceph
> clusters deployed and running smoothly in PRODUCTIONS and countless in
> testing / pre-production.
>
> Since you are facing problems with your ceph testing , it does not mean
> CEPH is unstable.
>
> I would suggest put some time troubleshooting your problem.
>
> What i see from your logs --
>
> 1) you have 2 Mons thats a problem ( either have 1 or have 3 to form
> quorum ) . Add 1 more monitor node
Just to clarify this point a bit, one doesn't need an odd number of
monitors in a ceph cluster to reach quorum. This is a common misconception.
The requirement to reach quorum is simply to have a majority of monitors
able to talk to each other. If one has 2 monitors and both are able to
talk to each other they'll be able to form a quorum.
Odd-numbers are advised however because one can tolerate as much
failures with less infrastructure. E.g.,
- for n = 1, failure of 1 monitor means loss of quorum
- for n = 2, failure of 1 monitor means loss of quorum
- for n = 3, failure of 1 monitor is okay; failure of 2 monitors means
loss of quorum
- for n = 4, failure of 1 monitor is okay; failure of 2 monitors means
loss of quorum
- for n = 5, failure of 2 monitors is okay; failure of 3 monitors means
loss of quorum
- for n = 6, failure of 2 monitors is okay; failure of 3 monitors means
loss of quorum
etc.
So you can see how you don't get any benefits, from an availability
perspective, by having either 2, 4 or 6 monitors when compared to having
1, 3, 5. If your target however is replication, then 2 is better than 1.
-Joao
--
Joao Eduardo Luis
Software Engineer | http://inktank.com | http://ceph.com
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Umar Draz
Network Architect
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