Quote: Originally Posted by fakeasdf
This is good information to know! I'm surprised prefetch is disabled tho, it seems even with the rocking speeds of SSD's, RAM speeds still destroy them when it comes to transfer rates, especially due to the SATA 2 controller limits. I guess maybe it's a minuscule gain and not worth letting your system worry about it? I dunno..
Prefetch is not the same thing as superfetch. I'm guessing you're thinking of the latter.
Prefetch is essentially a disk optimisation mechanism. It monitors which fragments of which executable files are commonly used together, and then causes them to be laid out next to each other on disk, even if it means the layout doesn't make much sense to the casual observer.
(Incidentally, that's why 3rd-party non-prefetch-aware disk defraggers can sometimes mess up the on-disk layout and slow things down, but that's a different story.)
SSDs have extremely low seek times and no rotational delay, so access times are uniform irrespective of "where" on the disk a particular fragment is to be found; in fact, "where" is almost non-sensical when using an SSD. Prefetch therefore loses its main raison d'etre
. (There is another one, but it's minor and too involved to explain.)
Superfetch is a predictive RAM pre-population thing. Instead of having unassigned RAM stay totally useless, superfetch fills it with stuff it thinks might be useful in the near future, based on past observation of that machine's usage patterns. No direct link to the disk or to prefetch. They just like using silly names