A long time ago, in a land far away, there lived a kernel that couldn't
handle UDMA hard disks... (20th century fox fanfare, spaceship fades
in...)
That was with kernels prior to 2.0.34, and one needed to disable the DMA
option on hard disks just to be able to boot.
These days, kernels from the 2.2 series can handle such hard disks just
fine. Except that the DMA options is turned OFF by default in *every*
distribution kernel I have seen installed (also in the kernel defaults as
shipped by Dr.Torvalds). Appears that there are issues with some older
hardware that Linus is not willing to take responsibility for...
Sadly, this can have give you some serious performance hits if you use IDE
disks. For example, my xmms starting skipping while some serious disk
activity was going on.
The solution is to turn on DMA usage by default for your hard disk.
However, beware - if you have funky hardware, you are going to call your
lawyers.
So, to find out if you will survive *and* to see the effect of having DMA
turned on, run
hdparm -d1 /dev/hd?
where ?=a/b/c/d (whichever drive you want to affect)
Run your system normnally for a while. If you see *any* problems that
weren't there before, turn the option off
hdparm -d0 /dev/hd?
If you see no problems, you can get to turn it on automatically at kernel
level by setting CONFIG_IDEDMA_AUTO to "y" when you configure your kernel
before compiling.
Oh BTW - don't bother sending you lawyers after me if this tip doesn't
work for you, if your dog bites you or if your disk crashes. It works for
me (xmms no longer skips when I have major disk activity going on), but
your milage may vary.
You have been warned.
Atul
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Atul Chitnis | [EMAIL PROTECTED] (PGP:6011BCB8)
C&B Consulting | http://www.cbconsulting.com
Bangalore, India | +91(80)3440397 Fax +91(80)3341137
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