<br><br><div class="gmail_quote">On Thu, Apr 8, 2010 at 2:19 PM, Olivier Le Cam <span dir="ltr"><<a href="mailto:Olivier.LeCam@crdp.ac-versailles.fr">Olivier.LeCam@crdp.ac-versailles.fr</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi -<div class="im"><br>
<br>
Raghavendra G wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Well, as far as I understand the problem is rather that folders on<br>
the path of the targeted file are not cached at all by io-cache. <br>
<br>
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.<br>
</blockquote>
<br></div>
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.</blockquote><div><br>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.<br>
<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="im"><br>
<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
This is why accessing a file makes (quite a lot) network traffic and<br>
can introduce bottlenecks because each folder is stated on the<br>
servers before delivering the file, even if that file is indeed<br>
cached by io-cache.<br>
<br>
<br>
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.<br>
</blockquote>
<br></div>
Well I know understand that I don't have to focus my attention on io-cache at all anymore.<br>
<br>
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!<br>
<br>
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!<br>
</blockquote><div><br>Did you try with a very high cache-timeout value (say 5 minutes or more)? Also a bigger cache-size might help.<br> <br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<br>
Hope you can put me on the right way, please!<div><div></div><div class="h5"><br>
<br>
Thanks and best regards,<br>
-- <br>
Olivier<br>
<br>
<br>
_______________________________________________<br>
Gluster-devel mailing list<br>
<a href="mailto:Gluster-devel@nongnu.org" target="_blank">Gluster-devel@nongnu.org</a><br>
<a href="http://lists.nongnu.org/mailman/listinfo/gluster-devel" target="_blank">http://lists.nongnu.org/mailman/listinfo/gluster-devel</a><br>
</div></div></blockquote></div><br><br clear="all">regards,<br>-- <br>Raghavendra G<br><br>