Running a 'medium' EC2 instance

[John Arbash Meinel]

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After investigating the test failures on our EC2 machine, I did start up
a "Medium" cpu instance. The main difference is that the new instance
has 2 faster processors.

On that machine, I don't get any of the "spurious" failures, even
without my file.close() patch. (At least, I haven't gotten them after 6k
tests.)

I was looking at the pricing, and it seems the Medium Windows instances
cost $0.29/hr rather than $0.12/hr. Which comes out to $208/mo rather
than $90/mo.

I also saw that Amazon offers "Reserved Instances", where you pay $X up
front, and then get to run cheaper per-hour. The pricing for a 1 year
reservation is such that you break-even at ~6 months of constant uptime.
I didn't specifically see a Windows option, though. The savings for 1
year of solid uptime is approx 1.5:1.

I'd certainly like to get things working on a single-CPU machine, but it
doesn't seem like the best use of my time.

So one alternative is to get everything set up so that we can start and
stop these instances on demand. Certainly I would expect to use far less
than 24x7 of the instance. More like 8x1 or so. Which would drop the
monthly cost to something like $10/mo even for the medium cpu instance.

I was also wondering how we could hook up this sort of thing to
buildbot/hudson. I believe Vincent mentioned that hudson has support for
starting a slave, waiting for it to get ready, then having it run
commands, and then shut itself down. If that is true, then it seems like
a rather good fit for our usage. Running for 1-2hrs / day including
startup, running, and shutdown times seems quite reasonable.

It would also mean that starting up a build host wouldn't interfere with
the test suite running, since they could be run on separate instances.

What do you guys think? I don't think we want to pay $200/month to keep
a live server running. But is it worth the effort getting the ability to
start up instances on demand?

John
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