I've also seen highly variable io performance (ie, slow/stuck) on EBS volumes. Sometimes, all reads/writes block for several second or minutes, with iowait going to 100% on an m1.small.

example: http://developer.amazonwebservices.com/connect/message.jspa?...

However, I've decided that the other benefits of EBS volumes are just to important to give up on (snapshotting, lazy-load, re-attachment). Instead, I plan to monitor for such situations and blow away the node when I detect it.

But really, I don't understand why Amazon doesn't fix this. It's happened to me 3-4 times in a relatively small installation. Surely their monitoring can detect this?