Re: UDMA 100 / PIIX4 question

[Tim Moore]

> You should be able to get about 30 MB/s at the start of the disk (zone 0) according to IBM's datasheet at
> 
> http://ssdweb01.storage.ibm.com/techsup/hddtech/prodspec/dtla_spw.pdf
> 
> so if you were testing say /dev/hda1 which is at the start of the disk it should be faster.

"should be" is yes and yes, but you will not see 30MB/s and there is no actual difference between
/dev/hda and /dev/had1.

> Try hdparm -i /dev/hda (or whatever) .. . note the reported MaxMultSect= value,
> and put it in place of X in command:
> 
> hdparm -u 1 -d 1 -m X -c 1 /dev/hda

I've spent more time with real world data transfer testing than god, both PIIX4-based motherboards
and network based (Network Appliance <-> linux).  The only hdparm parameter that makes any
measurable, significnat difference for most modern drive and chipset combinations is -d1 and the
correct UDMA mode.

Try partitioning your disk in 4 equal segments and run multiple tests in runlevel1 on /dev/hda[1-4]
for '/usr/bin/time hdparm -tT' plus permutations of -a[0248]c[013]m[024816]u[01],
and /usr/bin/time dd if=/dev/hda[1-4] of=/dev/null bs=1k count={32,64,128,256,512,1024}k.

rgds,
tim.
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