[Discuss] AWS Linux server scaling question

[darose at darose.net (David Rosenstrauch)]

Couple of suggestions:

1) We don't really use Micro instances for anything in production. 
Smallest instances we use generally are m1.large, and most of our boxes 
are m1.xlarge or bigger.

2) IIRC, most of the AMI's out of the box are not configured with swap 
space.  So if the box starts to max out on memory conceivably bad things 
can happen.  Might be something to look into changing.

HTH,

DR

On 03/21/2013 11:58 AM, Drew Van Zandt wrote:
> Up front: While I'm solid on Linux for personal use, and use it daily, and
> have been sysadmin for a tiny company with just one internal server, I've
> never been what I consider a "real" sysadmin.
>
> I'm working with an all-volunteer group trying to figure out what our
> cheapest AWS setup to handle things for ~3500 users is.  Right now the
> webserver, which is basically just a Wordpress install, is running on a
> Micro instance.  When we released a half dozen documents that everyone
> wanted right away last week, of course it fell over a couple of times,
> (slow, nonresponsive, reboot needed once, etc.)  I joined the tech team
> pretty much the day before this happened.
>
> memcached was added sometime during the explosion.
>
> We're regrouping for next time this happens, and given the limited admin
> experience of everyone on the team, there are some disagreements on the
> best approach.  I'll present a few of the options under discussion, if
> anyone cares to comment I'd be happy to hear discussion.
>
> Option A:
> * Upgrade to a Small instance (1.7GB instead of 610MB)
> * Tune apache prefork config so the max number of clients does not cause
> much swapping at full load
> * Tune Apache: FollowSymlinks, AllowOverrides None (symlinks is security
> risk, accepting that)
> * Add indexes for any SQL query WHERE clauses that are common to the setup
> * Tune PHP and MySQL a bit for the limited available memory
>
> Option B:
> * Use several micro instances with load balancing
> * Apache/PHP/SQL tuning identically per instance
>
> Option C:
> * Two Small instances
> ** One runs Apache/wordpress
> ** One runs MySQL and lighttpd for static files (lighttpd may be
> unnecessary complexity)
> ** Each optimized as per A
>
> Other items considered:
> Amazon S3 for static files
> AWS DB-specific instance for SQL
> Medium instance
> Varnish
> 113 other caching solutions
>
> Based on making embedded Linux handle things with tiny, tiny memory models,
> I'm inclined to think that A would suffice for the load I expect folks to
> throw at it - the only reason even the Micro instance couldn't mostly
> handle it is that it had stock settings on everything, no tuning at all.  A
> Small instance is more than enough.
>
> Based on having survive office politics for years, I'm inclined to think
> that C is perfect, we're likely to get budget since Things Just Happened,
> and it should be able to handle loads far beyond what I ever expect our
> users to throw at it.  (Though we do get surges of 500+ users at high
> activity for a few days just before conventions...I would expect C with
> tuning to handle even that pretty gracefully.)
>
> In either A or C I'm inclined to ask for an identical config but with Micro
> instances for release prestaging/testing, I should be able to stress those
> with just a script on my server, and test load handling - the Small version
> should be strictly (and vastly) better than the prestaged test.
>
> Are we thinking along the right lines?
>
> *
> Drew Van Zandt
> Cam # US2010035593 (M:Liam Hopkins R: Bastian Rotgeld)
> Domain Coordinator, MA-003-D.  Masquerade aVST
> *
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