What does IOPS (in Amazon EBS) mean in practice?

Question

I have some images needed for an app. There are many images (50,000+) but the overall size is small (40 Mb). Initially, I thought I would simply use S3 but it is painfully slow

Answer 1

@Mark B's answer is probably correct, in that it points out your IOPs are based on the size of your EBS volume. For what you want, S3 is the best option.

But depending on your use case and requirements, EBS may be needed. This is especially true if you want to run a database. In that case, you have a couple of options.

You can get Provisioned IOPS - if you know you need 5000 IOPS, but only need say 100GB of storage (which with gp2 would normally provide you with around 300 IOPS), you can use io1 volumes. There is an extra cost to this, and you'll want to make sure that it's attached to an EBS optimized instance, but you can get up to 20k IOPS if needed.

If you're doing a lot of sequential reads (reading in a large data set?) then there's a new type of EBS, st1. This is good for 500MB/s, and is less than 1/2 the cost of gp2.

Finally, there's one other scenario you could consider (say, you're a bit of a madman, and want to try doing strange things). If you can grab an archive from somewhere, and all you care about is serving them up from a really fast file system, you could put them on an instance that has instance storage. This is a locally-attached SSD, so it's very fast. The only drawback is that when your instance stops, you data is gone.

To address your update, "how many IOPS do you need for a database", the answer is "it depends". Every database engine has different requirements, and every database use has different usage patterns. Take a look at this if you want more information. But basically, test & monitor. If you're worried, over provision at launch, and scale down as needed. Or take a guess, and increase if you run into problems - is it more important to minimize costs, or provide good performance to your end users?