[TriLUG] Re: load shooting up on large sequential copies

[Sean Estabrooks]

On Tue, 02 Sep 2003 13:13:19 -0400
Marvin Blackburn <mblackburn at glenraven.com> wrote:

> We have a problem where the load shoots up as well as sys cpu when we do
> some large sequential copies.
> We are copying two 500MB files from point a to point b.  Both filesystems
> are ext3 on raid 5.
> 
> Does anyone have any ideas on what kernel tuneables might help with this
> problem, or what mount options my be helpful.
> Thanks.
> 

Hi Marvin,

     Are you using IDE drives ?   Have you made sure that DMA is enabled 
on them ?   If not all such copies have to pass through the CPU and you'll
see the kind of load you're talking about.    The command:

hdparm /dev/hda

(substitute proper drive name) will tell you if this is the case.   To enable DMA
on this drive:

hdparm -d1 /dev/hda

Cheers,
Sean