System slowdown on large disk writes

[Jamon Camisso]

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.

Is this with the kernel that you were compiling and had a question about 
DMA? Did you ever get that problem resolved? Doesn't sound like it would 
be a problem, but I'm curious in a general sense as to how something 
like that could affect I/O operations.

Jamon
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