[Samba] CTDB NFS setup?

[Volker Lendecke]

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

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