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Am 05.05.2011 16:26, schrieb Mike Franon:
<blockquote
cite="mid:BANLkTiko=RgeKFExHxgFKL-ArTxnrACoVA@mail.gmail.com"
type="cite">
<pre wrap="">Has anyone run multiple instances of varnish on the same server and
how is the performance overall?
I am looking into it, because I want to serve up the same url, but
depending if it is a bot go to a different backend.
I am trying to figure out the best way to do that.
</pre>
</blockquote>
<br>
Hi Mike,<br>
although I am not completely understanding your motivation I still
can state<br>
that my current customer had two varnish instances running on
several machines.<br>
Therefore it works :)<br>
<br>
The reason was not to run out of file descriptors (I was told...)<br>
Meanwhile I migrated every two instances to a single instance per
machine.<br>
<br>
Well, performance (with two instances) was ok when you have cpu in
mind. <br>
On the other hand it's not very effective to have the same objects
in two different caches <br>
because virtual memory (and/or file cache of course) isn't shared
between both instances.<br>
This results in a lower hitrate and the double number of backend
requests.<br>
<br>
Technically you have to setup two instances using different instance
names<br>
using the -n parameter and of course different ports to listen on
(client req and cli).<br>
<br>
A reasonable setup would be to split domain names at the load
balancer and feed<br>
them to different varnish instances - those could be run on same
hardware.<br>
On the other hand you double your overhead memory usage (cache
fragmentation,<br>
spare threads and such).<br>
<br>
I personally see no reason why to run more than one varnish instance
on the same<br>
hardware and I think you can do everything in VCL.<br>
<br>
Stefan<br>
<br>
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<p class="FONT8B"><b>Dipl.-Inform. Stefan Pommerening<br>
Informatik-Büro: IT-Dienste & Projekte, Consulting &
Coaching</b><br>
<a href="http://www.dmsp.de/">http://www.dmsp.de</a></p>
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