From: Trond Myklebust <trond.myklebust@fys.uio.no>
Subject: Re: NFS cache problem
Date: Wed, 25 May 2005 22:12:14 -0400
Message-ID: <1117073534.10938.6.camel@lade.trondhjem.org>
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Cc: nfs@lists.sourceforge.net
To: Anton Starikov <A.Starikov@utwente.nl>
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to den 26.05.2005 Klokka 02:29 (+0200) skreiv Anton Starikov:
> Trond Myklebust wrote:
> > "noac" just means that the client rereads the attributes every time it
> > reads or writes.
> > If the size and the mtime on the file haven't changed, then the client
> > assumes the data in the file itself also hasn't changed. That is usually
> > a good assumption on something like XFS (which has nanosecond precision
> > on mtime). It can be rather inaccurate on something like EXT3 (which has
> > a precision of only 1 second on mtime).
> I use ReiserFS.
> And here we talk not about seconds...we talk about hours sometimes.
> That's seems too strange for me. For seconds I can find plenty of
> explanations :)
> In principal even if it will be one minute, I'll be much more happy than
> now.

I repeat: if the file attributes do not change, then the NFS client will
not update its data cache. That is true of Solaris too.

> > If you seriously need uncached reads and writes, then you should rather,
> > consider using O_DIRECT.
> Unfortunatelly this is not trivial problem. A lot of software are
> involved here. And I beleive that NFS should be able to work in this
> conditions properly. At least it did with solaris in similar environment.

Mind describing _what_ kind of environment it works under? In other
words, what is the Solaris client doing that the Linux client is not
doing when running under the _same_ conditions (i.e. against the same
server and running the same applications)?

Cheers,
  Trond


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