System slowdown on large disk writes

Jason Shein jason-xgs8i/e9EeWTtA8H5PvdGCwD8/FfD2ys at public.gmane.org
Thu Mar 2 22:08:09 UTC 2006


On Thursday 02 March 2006 16:25, William O'Higgins Witteman wrote:
> 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.

Have you considered benchmarking the drive to see how it performs?

Here is a good multi-platform filesystem benchmarking utility.
http://www.iozone.org/

Builds for: AIX, BSDI, HP-UX, IRIX, FreeBSD, Linux, OpenBSD, NetBSD, OSFV3, 
OSFV4, OSFV5, SCO OpenServer, Solaris, Windows95/98/NT

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Jason Shein
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