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Re: PATA System Slowdown

John Baab wrote:
> I am experiencing a system slowdown when moving files between my SATA
> and PATA drives.  CPU usage jumps to 100% and the system is basically
> unusable.  The problem does not exist when I am only using the SATA
> drive, only when I use the two of them.  I am running an Asus K8V
> Deluxe SE board, using the VIA SATA.  Anyone have any ideas?
> -Thanks, John

Do you have DMA enabled?

# hdparm -d /dev/hda

If your DMA is disabled, there are two likely reasons.

1. Sometimes the kernel disables DMA when it detects an error; check
your kernel logs. If that's what happened, you may or may not be able to
re-enable it safely with 'hdparm -d1 /dev/hda'. By "safely" I don't mean
"your hard drive might catch fire", but rather that the worst I've seen
happen is that processes accessing the drive go into uninterruptible
sleep and you have to reboot. Or, sometimes the kernel disables DMA
again a few seconds later. Unless you actually have a failing hard
drive, though, turning DMA back on shouldn't be a problem; with a couple
of the motherboards I used to have, the kernel would disable DMA on a
drive once every few months and I was always able to re-enable it

2. If trying to re-enable DMA with hdparm spits out an error (I don't
remember the wording) then probably you don't have support for your IDE
chipset compiled into the kernel. Once you do that, DMA will be enabled
automatically on boot.


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