On Thu, Apr 8, 2010 at 2:19 PM, Olivier Le Cam < [email protected]> wrote:
> Hi - > > > 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. >> > > 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. 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. > > 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. >> > > Well I know understand that I don't have to focus my attention on io-cache > at all anymore. > > 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 > > > _______________________________________________ > Gluster-devel mailing list > [email protected] > http://lists.nongnu.org/mailman/listinfo/gluster-devel > regards, -- Raghavendra G
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