Originally Posted by Totoro
This is what I meant. Drive does it automatically, costs +/- 50% more vs. straight up HDD.
Agree 100%. I know you know this, but for some others, that haven't had exposure.
It's a concept that's been in use on enterprise class disk for a long time, but an order of magnitude more cache. As you mentioned its automatic, exactly what is needed. Your hot data stays on ssd and is backed by hdd. In enterprise class sans, you(at least a year ago) paided extra for that feature.
The benefits of avoiding hdd hits improves performance, as your not mechanically seeking to a track and reading a sector. Even the fastest disk slows the cpu down to a crawl if you're waiting on i/o operations. With ssd that happens at memory transfer speed(more or less), a very short wait.
Many years ago(30) I was in a presentation given by a application tuning guy. His point was the cheapest i/o was the one you didn't do. His example was great, if a mainframe only executed a single instruction a second it would take one year for an i/o to complete. Most of that year (10+ months as I recall) was spend waiting on the disk. Technology is different but physical i/o, (waiting on disk) has always been a bottleneck.