2 ms·
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 goi
by recampbell 16y ago
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?messageID=201918#201918 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?
- dasil003 16y agoIs it because of the network throughput on the small instance type? I haven't noticed anything nearly that severe with our 20-instance setup of larger instance sizes, but then again we've only run production on EC2 for a few months now...
- moe 16y agoBut really, I don't understand why Amazon doesn't fix this. When you select your instance-type then you get to choose between "Low", "Moderate", "High" and "Very High" I/O performance. Want to take a guess at which instance types suffer first when there is high I/O demand or contention?
- recampbell 16y agoI can handle suffering, but completely freezing?
- moe 16y agoThat is likely not intended so I guess it's probably inherent to how Xen and/or their I/O layer do the resource allocation. I, too, have seen these freezes occasionally on small instances. If you think that is harsh then try one of the new micro's. ;-) Anyways, I haven't had such a freeze last longer than a minute yet, and the instance would always recover. If yours does not recover then that would clearly be a bug.