We have an m1.medium EC2 instance with a small (15G) EBS drive, running both Rails 3 and a PostgreSQL server. We've noticed CPU spikes at odd times, and finally realized that even simple, sustained EBS access seems to pin the CPU. For instance, just grepping about 3G of logs resulted in 100% CPU usage - which means both cores, which should be impossible for grep! Deleting a bunch of log files also used about 25% of the CPU, which is more than I'd expect. We're not swapping.
Is this normal? It's hard to Google for this, since "high CPU" is also the name of a type of EC2 instance. I'll happily provide more details and benchmarks, but first I wanted to check if this was a thing.