Messages in this thread | | | Date | Tue, 6 Mar 2001 13:45:54 +0000 | From | Jonathan Morton <> |
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>> 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
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