amcdiarmid's Journal: raid & av & memory

I think that if you have enough memory, I would not use the disk for tertiary storage. Just read the file into memory at once & scan the whole thing. But I suspect I don't know enough about it.

As far as Raid goes, I got the impression that you wanted to use a mirror to speed up disk reads - as opposed to a stripe (with no data redundancy).

If I understand correctly,

Raid 0 is fastest: JBOD data is broken in two parts and written to each disk in //. Reading is 1/2 from each disk and the fastest.

Raid 1 is a mirror and is the same speed as just one disk. (although you suggest it's a bit faster)

Raid 2-4 are (mostly) academic

Raid 5 (taking more than two disks) stripes the data across multiple disks and is almost as fast as Raid 0 for reads (you don't the speed advantage of one whichever disk has the parity stripe). It is also the slowest for writing as the (hopefully) coprocessor has to calculate the parity stripe and which disk it is going on.