Azure - Extra small instance web role - ready for production?

Question

I'm planning for a website running in Azure. I'm estimating max. 2000 users a day creating about 20.000 hits.

I know I'm kinda vague here, but is the extra small instance ready for this kind of site? I'm using MVC 3 to create the site. Thanks for any answers.

Answer 1

You'd have to do some load-testing to best judge that question. Remember that, to enjoy the benefits of Windows Azure Compute SLA, you'll need a minimum of 2 instances (so now you have instances in different fault domains, so your site remains running even if one of the instances recycles due to OS upgrade, hardware failure, etc.). The question then becomes: can two Extra Small instances handle 20,000 hits daily? This equates to approx. 10K hits per VM instance per day, or 416 hits per hour, or 7 per minute. And... even with one instance, a hit rate of 14 per minute is fairly low.

More than CPU, you might find yourself bottlenecked by bandwidth, since you'll only see about 5Mbps per instance, vs. around 100Mbps per Small instance.

You might want to run a quick test with something like LoadStorm, which provides Load Testing as a Service. This should give you a good idea of how well the XS will perform under load.

EDIT (March 2012): Extra Small instances are now $0.02 / hour vs $0.04, so you could run up to 6 XS instances for the same cost of a single Small. This makes the XS option even more compelling. See this blog post for the official announcement on the price drop (including Storage cuts as well).

Answer 2

I agree with David that this is very dependent on the load per request you generate (both in CPU and bandwidth resources)

I just wanted to share our own experience with the XS instances. We've found that these instances suffer from severe clock drift: http://blog.codingoutloud.com/2011/08/25/azure-faq-how-frequently-is-the-clock-on-my-windows-azure-vm-synchronized/

This could be as much as a minute of difference over the week between NTP syncs. For most applications this isn't necessarily a problem, but we used Oauth1.0a authentication with an allowed timestamp difference of 30 seconds which resulted in major headaches when using XS. The S and larger don't have shared cores and consequently suffer much less clock drift.

Answer 3

You get a better SLA with 2 small instances rather than 1 larger.

You should also look at your peak load. For example with 20,000 hits per day, do 50% come between 9 and 10 in the morning?

Instance storage is 20GB, if this is just your application code should not be a problem.

IO performance is low, if this is just reading your app code first time it compiles should not be a problem.

CPU single 1 GHz, if this is just web pages and little calculation should not be a problem. The time this will be really slow is during a JIT compile.

The memory is 768 MB, this could be a problem especially if you are caching data.

You save under 2 USD a day using the small instance. But that is a Latte every 2 days so maybe it is worth taking the risk and having to do an extra deploy.