samba - Mar 2012 - CTDB NFS setup?

Hello,

I try to set up a clustered samba server (on Novell SLES11SP2) based
upon CTDB and NFS. My problem is that I do not yet understand the
structure of the setup when using NFS.

I followed the documentation in

http://wiki.samba.org/index.php/CTDB_Setup#Setting_up_CTDB_for_clustered_NFS

As far as I understand this documentation, it should be possible to set
up a samba cluster say having 3 nodes where I can use NFS instead of a
cluster filesystem like OCFS for the shared data directory that ctdb needs.

My initial thought was that I have exactly one NFS share (provided by
one NFS server)  and each node of the cluster mounts this directory to
access shared data but the documentation speaks explicitly of "each
cluster node exporting a share" with the same NFS fsid which I cannot
understand.

The config of CTDB again has parameters that allow the configuration of
the path where the shared (NFS) directory can be found that ctdb should
use. Aside from this ctdb has scripts and parameters that allow it to
automatically start/stop services like nfs and smb. So what do I have to
configure manually and what is done by ctdb's scripts?

What I cannot understand is who mounts all the export directories of the
cluster nodes? Does ctdb do this by some magic? Where can I tell ctdb
where these directories should be mounted.

Is it after all possible to use a simple NFS share as a shared directory
for CTDB or do I really need a real cluster filesystem klike OCFS2?

Can anyone help?

Have a nice day
Rainer
-- 
Rainer Krienke, Uni Koblenz, Rechenzentrum, A22, Universitaetsstrasse  1
56070 Koblenz, http://userpages.uni-koblenz.de/~krienke, Tel: +49261287 1312
PGP: http://userpages.uni-koblenz.de/~krienke/mypgp.html,Fax: +49261287
1001312

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On Thu, Mar 22, 2012 at 01:16:18PM +0100, Rainer Krienke
wrote:
> Hello,
> 
> I try to set up a clustered samba server (on Novell SLES11SP2) based
> upon CTDB and NFS. My problem is that I do not yet understand the
> structure of the setup when using NFS.
> 
> I followed the documentation in
> 
>
http://wiki.samba.org/index.php/CTDB_Setup#Setting_up_CTDB_for_clustered_NFS
> 
> As far as I understand this documentation, it should be possible to set
> up a samba cluster say having 3 nodes where I can use NFS instead of a
> cluster filesystem like OCFS for the shared data directory that ctdb needs.
> 
> My initial thought was that I have exactly one NFS share (provided by
> one NFS server)  and each node of the cluster mounts this directory to
> access shared data but the documentation speaks explicitly of "each
> cluster node exporting a share" with the same NFS fsid which I cannot
> understand.
> 
> The config of CTDB again has parameters that allow the configuration of
> the path where the shared (NFS) directory can be found that ctdb should
> use. Aside from this ctdb has scripts and parameters that allow it to
> automatically start/stop services like nfs and smb. So what do I have to
> configure manually and what is done by ctdb's scripts?
> 
> What I cannot understand is who mounts all the export directories of the
> cluster nodes? Does ctdb do this by some magic? Where can I tell ctdb
> where these directories should be mounted.
> 
> Is it after all possible to use a simple NFS share as a shared directory
> for CTDB or do I really need a real cluster filesystem klike OCFS2?
In general, strongly advise against exporting NFS imports
via Samba.

Moreover, NFS does not provide the same consistency
guarantees that a proper cluster file system does and that
Samba/CTDB expects. The basic test for this is tridge's
ping_pong program

https://junkcode.samba.org/ftp/unpacked/junkcode/ping_pong.c

You should try that with -rw on your NFS setup.

With best regards,

Volker Lendecke

-- 
SerNet GmbH, Bahnhofsallee 1b, 37081 G?ttingen
phone: +49-551-370000-0, fax: +49-551-370000-9
AG G?ttingen, HRB 2816, GF: Dr. Johannes Loxen
http://www.sernet.de, mailto:kontakt at sernet.de