System slowdown on large disk writes

William O'Higgins Witteman william.ohiggins-H217xnMUJC0sA/PxXw9srA at public.gmane.org
Thu Mar 2 21:25:16 UTC 2006


On Thu, Mar 02, 2006 at 03:03:51PM -0500, Lennart Sorensen wrote:
>On Thu, Mar 02, 2006 at 01:17:50PM -0500, William O'Higgins Witteman wrote:
>> I'm copying 500Mb to 4Gb files to another location on the same ext3
>> (I think - how would I check?) 140-odd Gb partition.
>
>I believe the default io schedular in 2.6 kernels is designed to handle
>random io pretty nicely, but can be pretty unfair if doing lots of
>sequential I/O.  Perhaps trying another io scheduler, or tuning it a bit
>(it should have options in /sys or /proc somewhere) could make it
>better.

Eeek.  Okay, I've never poked into that part of the filesystem before.
I get to learn something new.

>Does it make all io sluggish or just other io to the same drive?

It seems to be only when it is reading and writing off the same drive -
if I've pulling all the data off a DVD there is no such slowdow.

BTW, I looked at smartctl and dmesg, and there are no errors, so it's not
likely a bad drive.
-- 

yours,

William

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