Note that throughput is not everything : some of those options don't
affect throughput much, but they reduce "system time" i.e. time spent in
kernel mode for interrupt handling etc. This is a big win since some other
process could run in the time which otherwise would be spent in disk I/O.
The following very rough measurement was done on a P-100 8MB IDE Seagate
ST31276A, kernel 2.0.29 with the Triton stuff, after booting with
init=/bin/bash. I haven't averaged or anything, but these are fairly
representative :
With default settings (everything off except readahead)
time hdparm -t /dev/hda
Throughput 3.66 MB/sec
Time 0.06user 3.55system 0:07.31elapsed 49%CPU
No. of ide0 interrupts 32810
With hdparm -c1 -m16 -d1 -X34 /dev/hda
Throughput 4.69 MB/sec
Time 0.04user 0.88system 0:06.59elapsed 13%CPU
No. of ide0 interrupts 260 !!
This is a HUGE order of magnitude improvement ! This deserves to be better
documented ... right now it's just in the hdparm manpage AFAIK. I don't think
too many people know about this ...
-- ganesh