Re: How to improve db performance with $7K?

"Matthew Nuzum" <matt(dot)followers(at)gmail(dot)com> writes:
> So if you all were going to choose between two hard drives where:
> drive A has capacity C and spins at 15K rpms, and
> drive B has capacity 2 x C and spins at 10K rpms and
> all other features are the same, the price is the same and C is enough
> disk space which would you choose?

> I've noticed that on IDE drives, as the capacity increases the data
> density increases and there is a pereceived (I've not measured it)
> performance increase.

> Would the increased data density of the higher capacity drive be of
> greater benefit than the faster spindle speed of drive A?

Depends how they got the 2x capacity increase. If they got it by
increased bit density --- same number of tracks, but more sectors
per track --- then drive B actually has a higher transfer rate,
because in one rotation it can transfer twice as much data as drive A.
More tracks per cylinder (ie, more platters) can also be a speed win
since you can touch more data before you have to seek to another
cylinder. Drive B will lose if the 2x capacity was all from adding
cylinders (unless its seek-time spec is way better than A's ... which
is unlikely but not impossible, considering the cylinders are probably
closer together).

Usually there's some-of-each involved, so it's hard to make any
definite statement without more facts.

regards, tom lane