Re: scsi vs ide performance on fsync's

Jonathan Morton
2001-03-06T13:47:02Z

>> i assume you meant to time the xlog.c program? (or did i miss another
>> program on the thread?)

Yes.

>> i've an IBM-DJSA-210 (travelstar 10GB, 5411rpm) which appears to do
>> *something* with the write cache flag -- it gets 0.10s elapsed real time
>> in default config; and gets 2.91s if i do "hdparm -W 0".
>>
>> ditto for an IBM-DTLA-307015 (deskstar 15GB 7200rpm) -- varies from .15s
>> with write-cache to 1.8s without.
>>
>> and an IBM-DTLA-307075 (deskstar 75GB 7200rpm) varies from .03s to 1.67s.
>>
>> of course 1.8s is nowhere near enough time for 200 writes to complete.
>
>hi, not enough sleep, can't do math. 1.67s is exactly the ballpark you'd
>expect for 200 writes to a correctly functioning 7200rpm disk. and the
>travelstar appears to be doing the right thing as well.

I was just about to point that out. :) I ran the program with 2000
packets in order to magnify the difference.

So, it appears that the IBM IDE drives are doing the "right thing" when
write-caching is switched off, but the Seagate drive (at least the one I'm
using) appears not to turn the write-caching off at all. I want to try
this out with some other drives, including a Seagate SCSI drive and a
different Seagate IDE drive (attached to a non-UDMA controller), and
perhaps a couple of older drives which I just happen to have lying around
(particularly a Maxtor and an old TravelStar with very little cache).
That'll have to wait until later, though - university work beckons. :(

--------------------------------------------------------------
from: Jonathan "Chromatix" Morton
mail: chromi@cyberspace.org (not for attachments)
big-mail: chromatix@penguinpowered.com
uni-mail: j.d.morton@lancaster.ac.uk

The key to knowledge is not to rely on people to teach you it.

Get VNC Server for Macintosh from http://www.chromatix.uklinux.net/vnc/

-----BEGIN GEEK CODE BLOCK-----
Version 3.12
GCS$/E/S dpu(!) s:- a20 C+++ UL++ P L+++ E W+ N- o? K? w--- O-- M++$ V? PS
PE- Y+ PGP++ t- 5- X- R !tv b++ DI+++ D G e+ h+ r- y+
-----END GEEK CODE BLOCK-----