[Gluster-devel] lookup caching

Raghavendra G raghavendra at gluster.com
Sat Apr 3 13:10:42 UTC 2010

On Fri, Apr 2, 2010 at 3:32 PM, Olivier Le Cam <
Olivier.LeCam at crdp.ac-versailles.fr> wrote:

> Hi -
> I am evaluating glusterfs for a replacement of an NFS server which acts as
> a backend storage for a webcluster, in order to take advantage of its very
> interesting features in term of high-availability and scalability.
> That said, I'm experiencing (like everybody in the same situation)
> performance issues due to the large number of small files a webserver have
> to deal with.

> The io-cache translator does not help so much in this situation because (as
> far as I understood) the clients always have to check the mtime of the
> target file before delivering it in order to known if the cache is
> up-to-date. This intensive network traffic is quite penalizing in term of
> performance (especially on a Gb-E).

> Following to a recent talk on the IRC channel, it came to my mind that
> caching lookups could (in this particular situation) greatly improve the
> performances.

If you are not very much concerned about file being changed from other
clients while it is being cached, you can set 'cache-timeout' value in
io-cache configuration to some high value, there by increasing the time
intervals at which stat call is sent to server to check whether the file has

> I have observed the GlusterFS code carefully and TBH I haven't been able to
> see how/where such a translator could be integrated in.
> Would it be possible to get some help? Are other users/developers already
> involved in such a development?

If you are just interested in caching stats for beniefit of io-cache, the
same functionality can be achieved by tuning cache-timeout value in

> I don't want to bother you more than necessary, getting few advices would
> be enough in order to put me on the way.
> I'll appreciate any comments or pointers.
> Thanks and best regards,
> --
> Olivier
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Raghavendra G
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