> SSDs are not a requirement: one can get equivalent system performance, with predictable failures, by spending more money on more hard drives and CPUs to talk

> SSDs are not a requirement: one can get equivalent system performance, with predictable failures, by spending more money on more hard drives and CPUs to talk to them. Lots more money. Many, many more hard drives, with failure rates to match. And you're still not going to get there. We started running a 240TB all SSD array a few months ago and we get sub-millisecond latencies on most reads and writes. When we see an excursion to 10ms that's cause for concern; 50ms and we do a root-cause. We can peg multiple 16GBit fiber channels and it's okay. And it fits in half a rack; try that with disk. I cannot imagine doing this with spinning rust.