Displacing HDDs

Just for the record, we're serious about optimizing for SSD as well as HDD. A lot of optimizations apply to both, or at least, one doesn't hurt the other. Eventually there might be tuning parameters, if we hit any optimizations that are mutually incompatible. Optimizing for SSD is made a lot harder because everybody has their own FTL algorithm, we need to guess how they're trying to guess what we're trying to do, if you know what I mean. But writing less total data is always going to be a win on any device, and we think we're doing a pretty good job of that right now.