"Matthew Nuzum" <[EMAIL PROTECTED]> writes:

> 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?

In this case you always choose the 15k RPM drive, at least for Postgres.
The 15kRPM reduces the latency which improves performance when fsyncing
transaction commits.

The real question is whether you choose the single 15kRPM drive or additional
drives at 10kRPM... Additional spindles would give a much bigger bandwidth
improvement but questionable latency improvement.

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

actually a 2xC capacity drive probably just has twice as many platters which
means it would perform identically to the C capacity drive. If it has denser
platters that might improve performance slightly.


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