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

Greg Stark <gsstark@mit.edu> writes:
> In any case the issue with the IDE protocol is that fundamentally you
> can only have a single command pending. SCSI can have many commands
> pending.

That's the bottom line: the SCSI protocol was designed (twenty years ago!)
to allow the drive to do physical I/O scheduling, because the CPU can
issue multiple commands before the drive has to report completion of the
first one.  IDE isn't designed to do that.  I understand that the latest
revisions to the IDE/ATA specs allow the drive to do this sort of thing,
but support for it is far from widespread.

            regards, tom lane