Out of curiosity, as you apparently have some real data and real use-cases - have you benchmarked SSD vs disk for your use-case? In particular, do you still see a (comparable, or not) speed-up from better clustering of rows on SSD? (I would guess not, unless you have a lot of fragmentation at less than SSD write-size (typically 4k?) - and AFAIK postgres should already be trying to fix that for you, by how it lays out data on disk. But SSD do have somewhat better sequential read than random-read, even if not as dramatic as spinning disks).