[LRUG] Fwd: Server capacity

Gerhard Lazu gerhard at lazu.co.uk
Mon Mar 12 17:26:33 PDT 2012

... your* CPU usage ...

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---------- Forwarded message ----------
From: Gerhard Lazu <gerhard at lazu.co.uk>
Date: Tue, Mar 13, 2012 at 12:24 AM
Subject: Re: [LRUG] Server capacity
To: London Ruby Users Group <chat at lists.lrug.org>

80% is considered optimum capacity. You're not maxing out the server and
you're not wasting resources either. That's what VPS & cloud providers mean
when they say "we're so green that Amazon is a desert in comparison".

CPU and memory are not as much of a problem as disk usage. Disk iowait is
one to watch on shared disks. If your disks are doing anything above 5
%iowait (iostat -m 2), you're pushing them too much. sysstat with sar is a
good one to have. A lot of the time, when you're CPU usage is high, it's
usually network & disk iowait that are the root cause.

Put background jobs onto another machine, simple as. Heroku gives you 1 bg
worker for free. Each extra worker costs $0.05/h. As a rule of thumb, you
don't want to mix the *now* with *whenever*.


Twitter <http://twitter.com/#!/gerhardlazu> Github<https://github.com/gerhard>
 Blog <http://gerhardlazu.com/>

On Mon, Mar 12, 2012 at 4:11 PM, Andrew Stewart
<boss at airbladesoftware.com>wrote:

> Hola El Rug,
> What sort of capacity do people run their servers at?
> I have a Rails app on a 1-core Ubuntu 10.04 VPS with 1GB RAM.  Everything
> runs on that box: web server (Nginx), app servers (Unicorn with 5 workers),
> MySQL, background jobs etc etc.
> The RAM usage hovers at around 75%.  I want to make the most of what I've
> got; is 75% too conservative?  Adding another Unicorn worker would take the
> RAM usage to about 85%.  I wonder how much memory it's sensible to use up.
> Another thing: from time to time the app renders big PDFs with Prawn, and
> when this happens the CPU is maxed out for potentially several minutes,
> adversely affecting responsiveness.  What's a good way to address this?
> Thanks in advance.  Sorry this isn't a job ad ;)
> Cheers
> Andy Stewart
> -------
> http://airbladesoftware.com
> _______________________________________________
> Chat mailing list
> Chat at lists.lrug.org
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