On Mar 27, 2012, at 8:25 AM, Welty, Richard wrote:
does anyone have any tips on this? Linux Software Raid doesn't seem to be doing a very good job here, but i may well have missed something.
iostat -x 5 is your friend. We've been struggling with a similar setup recently, and the TL;DR summary is that EBS has unreliable performance and isn't acceptable to use when your performance matters. When it's rocking, a single EBS volume can get you ~1200 IOPs, but far too often, a volume will drop to less than 100 IOPS. And then there are the occasional times when they
almost lock up, but not entirely, so they lock up your raid but don't get automatically dropped (though you could drop them yourself).
When you have an 8-volume raid, you have 8x the exposure to these problems. We're coming to the realization that AWS has no real way to run a normal, non-memory resident database, and are looking to host our databases outside AWS using DirectConnect, or something similar. (And not to hijack this thread but if anybody has experiences with that, I'd love to hear them.)