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List:       varnish-misc
Subject:    Re: another architecture question
From:       Dridi Boukelmoune <dridi.boukelmoune () zenika ! com>
Date:       2014-08-20 16:52:02
Message-ID: CABtDKm4bzgVxrp76QTuHuH17O=zfT6daMft28qmCy7hTp3PVgA () mail ! gmail ! com
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Hi,

As a Java developer, I'd say that adding more RAM to a JVM may
probably incur longer GC pauses while on the other hand I'd trust
Varnish to gracefully scale with more RAM and CPU. Please do not
interpret that as a bad opinion on modern JVMs or Tomcat, you'd be
very wrong :-)

Architecture-wise, my first advice would be to think about removing
your httpd servers and put your Tomcat instances right behind Varnish.
Unless you need it for something other than a reverse proxy for your
webapp of course.

Regarding solutions a and b, my intuition goes towards b. Instead of
pinning one apache/tomcat pair for one Varnish instance, I'd put them
all in a director. If one backend is sick, Varnish can try again with
a healthy backend.

Performance-wise, measure, don't guess.

Cheers,
Dridi

On Wed, Aug 20, 2014 at 4:02 PM, Hernán Marsili <hernan@cmsmedios.com> wrote:
> Hi,
>
>
> A couple of month ago I asked a question here regarding the best VARNISH
> architecture for a high traffic site. We then do some testing and we are
> still unsure of the best scenario, so I ask again with a little more
> information.
>
> We have a 40.000 concurrent users sites. This is handled by 5 boxes. On each
> box we have TOMCAT, APACHE and VARNISH using malloc.
>
> What we want to determine, is the impact on each server VARNISH makes,
> mostly at a 'connections' level and determine if is best to:
>
> a) growth adding same kind of servers (boxes with all 3 services)
> b) separete Varnish from the boxes and have, for example, 2 varnishes
> balacing with 4 backend servers
>
> On the b scenario, we can assign more memory to the TOMCAT and handle more
> load. The CACHE HIT RATE is not an issue, since all the boxes have a very
> high hitrate.
>
> Any advice on this matter will be appreciated. We are inclining now for the
> A option.
>
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