[Samba] Slow Samba writes over NFS

[Volker Lendecke]

On Mon, Jul 21, 2008 at 11:14:59AM -0500, ashis.v.purbhoo at exxonmobil.com wrote:
> Thanks for the suggestions, putting Samba directly on the file server would
> be ideal, but due to the environment & the large number of Linux/Unix file
> servers, this is not a likely scenario.  Unfortunately, the only current
> option is for us is to use Samba accessing data over NFS.  From my
> understanding several factors went into deciding on Samba v2.0.10 and among
> that were NFS data integrity, smbd hanging and & non-use of *tdb's.  At
> some point in time we had to go from Samba v2.2 back to Samba v2.0.10 for
> the above reasons.
> 
> Suggestions received to speed NFS writes on Samba v3 vs. Samba v2:
>    Set "strict locking = no" (default in Samba v2*).  Default in Samba v3
>    is "strict locking = yes"
>    Set "posix locking = no"
>    The utimes(2) calls may have changed for write for correctness...

"strict locking" or even "locking" should not be touched.
"posix locking = no" is advisable for sharing NFS imports.

> With or without the suggested updates above, is Samba susceptible to NFS
> data corruption and smbd hangs?  Was the utime code/script update to really
> address NFS write correctness, or other?

The utimes stuff is not an NFS specific thing, the problem
though is that it is orders of magnitude slower over NFS
than on a local file system.

smbd hangs when re-exporting NFS are most likely NFS client
bugs that Samba can not work around. If smbd is stuck in D
state in a file system syscall like pread(2) or unlink(2),
there is NOTHING that Samba can do. This is a kernel issue.


> I need to determine if any/all of these items below have substance/still
> hold true for Samba v3* and specifically for Samba 3.0.27a.
>       Does these websites info. still hold true for Samba 3.0.27a?
>       http://threebit.net/mail-archive/samba/msg00821.html
>       Issues around Samba 3.0.5:
> 
>    http://www.usenet-forums.com/samba/308202-re-samba-exclusive-oplock-left-process.html

Beyond "posix locking = no" please also set "kernel oplocks
= no". Then depending on the quality of your NFS client
implementation you could get to a working server.

Volker
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