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.
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!
Hope you can put me on the right way, please!
Thanks and best regards,
--
Olivier
