IDE DMA problem [WAS: Re: Getting lousy NFS + tar-pipe throughput on 2.4.20]

[Timothy Miller <miller@techsource.com>]

I have discovered one major problem that I didn't think to check 
before.  I have never before had trouble using DMA with WD drives, VIA 
chipsets, or RH9, so I didn't think to check before, but hdparm reports 
that DMA is disabled for the disk on the workstation I mentioned in my 
earlier post.

So, I tried this:
    hdparm -d1 /dev/hda

And I got this result:
/dev/hda:
 Setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma = 0 (off)

How do I fix this?  Do I have to unmount the filesystem before I can 
change the dma setting?  Why would it be off to begin with?  I know that 
the BIOS is set up right.  Does 2.4.20 not work well with the KT600 chipset?

Thanks.


Timothy Miller wrote:
 > [snip everything about slow NFS performance]