On Thu, Apr 8, 2010 at 2:19 PM, Olivier Le Cam <Olivier.LeCam@xxxxxxxxxxxxxxxxxxxxx> wrote:
Metadata caching is done in stat-prefetch. But that is not suitable to your use-case. in stat-prefetch stats of dentries are stored from the period of readdir to close on directory fd.
Did you try with a very high cache-timeout value (say 5 minutes or more)? Also a bigger cache-size might help.
Hi -That's it. Metadata caching is exactly what I would like to implement but I haven't been able to find which part of code is dealing with metadatas so far.
Raghavendra G wrote:
Well, as far as I understand the problem is rather that folders on
the path of the targeted file are not cached at all by io-cache.
Did you mean caching dentries, when you said "caching directories"? io-cache only caches file data. Also note that it is not a translator which does metadata (stats) caching.
Metadata caching is done in stat-prefetch. But that is not suitable to your use-case. in stat-prefetch stats of dentries are stored from the period of readdir to close on directory fd.
Well I know understand that I don't have to focus my attention on io-cache at all anymore.
This is why accessing a file makes (quite a lot) network traffic and
can introduce bottlenecks because each folder is stated on the
servers before delivering the file, even if that file is indeed
cached by io-cache.
io-cache only sends stat on the file being read not to all of its parent directories. I am not getting the reason you are concerned with too many stat calls. io-cache (during read and when file is cached) only sends a single stat call and that too if "cache-timeout" number of seconds have been elapsed since last validation.
In order to reach acceptable performances for my webfarm (at least the same than I have with an NFS server), I really have to find a way for limiting as much as possible stat calls over the network. Stat calls introduce too much latency before the glusterfs client is able to deliver a file (even with io-cache enabled). This makes performances absolutly terrible!
Note: I'm not concerned at all by file being modified by other clients. The frontal reverse-proxy always forwards http connections to the same webserver (according to the domain name), but in case of failover. Having matadatas caching would then __greatly__ improve overall performance in this situation!
Did you try with a very high cache-timeout value (say 5 minutes or more)? Also a bigger cache-size might help.
Hope you can put me on the right way, please!
Thanks and best regards,
--
Olivier
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regards,
--
Raghavendra G
