On Sat, 2 Dec 2000, Cory Petkovsek wrote:
> I'm curious, has anyone gotten Ultra ATA/100 up and running on Linux
> (or win2k even)? I'd like to know real transfer speeds.
My 7200rpm ATA100 drive is pretty snappy at 66 so I have put that project
on a back burner.
> the 16-18mb on the 2100s. I called adaptec and complained, but the
> person I spoke with said, "well what is Ultra160 supposed to transfer
> at, I don't know....". I flashed the controller bios, but I think
If he'd said that to me I would have flashed him more than my controller
bios. "What color are brown dogs supposed to be?" "I don't
know...please...I'm trying...I'm just tech support...I tell you I don't
know..."
> Test your read speed under linux:
> ide only: (tests cache and disk reads, independently)
> hdparm -tT /dev/hda
I have so far not done any drive mods with HDPARM and I'm plugged into my
ATA66 instead of my ATA100 socket. Result of running above command:
[root@hitsquad /]# hdparm -tT /dev/hda
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.84 seconds =152.38 MB/sec
Timing buffered disk reads: 64 MB in 18.04 seconds = 3.55 MB/sec
>
> any drive:
> time dd if=/dev/sda of=/dev/null bs=1024 count=102400
> (returns minutes and seconds)
dd: /dev/sda: No such device
Command exited with non-zero status 1
0.01user 0.02system 0:00.11elapsed 25%CPU (0avgtext+0avgdata
0maxresident)k
0inputs+0outputs (269major+56minor)pagefaults 0swaps
Here's an idea (just a theory): High interface speeds are strictly to take
advantage of the maximum medium transfer rates -- the speeds you get from
the outermost tracks when a continuous atring of the exact data you want
happens to be under the read head at that moment. Track-to-track delays,
reading from anywhere except the outermost track, etc., all combine to
give you a lower average transfer speed. And isn't that what those drive
speed testers are telling you, average speed? Average speed should be
awfully smelly compared to max.
And I don't know much about RAID, but I read that some configurations let
you block off your innermost tracks, so you lose some storage space but
what you have left is fast.
-Chris
