I'm beginning to thing that MySQL does something very different with disks than Postgres, because everyone I've talked to that said they had a problem had been running MySQL, and everyone who has been successful has been running Postgres (myself included).
This really would not be all that surprising, but it also would not surprise me if the average Postgres setup was better tuned/architected than the majority case of MySQL uses.
Our setup was surely not ideal, but even with significant tuning, it was not sufficient.
It is really good to hear successes like Reddit's, though. How long have you folks had your databases in EC2?
Maybe. I know when we migrated Chesspark from native machines to EC2, the postgresql database performance was at least an order of magnitude worse, and we spent two weeks doing caching and index hunting that we never had to worry about before.
