[Techtalk] Software vs. Hardware RAID

Dave North dave at timocharis.com
Tue Aug 20 08:38:37 EST 2002

> 	It sounds a bit like I may have inadvertently stepped on your
> toes. Honest, I am at a loss.

Not at all! I think RAID is a moving target -- and just didn't want to let
it pass that one should not consider the software option when appropriate.
	Nor, of course, should hardware be overlooked when it is the best
	In trying to not respond to any particular post, perhaps I've
given the impression I was objecting to what you're up to. Nope!

> Just getting the thing working is the goal. At least for me.

I know the feeling.

> How does one get 7 IDE drives...1 CD, 1 CDRW, 4 HD drives,
> (and Now) 1-15gb, to work with only two Motherboard slots. I chose
> the only thing I knew, go with a PCI card w/two additional
> slots(channels). It seems it can be configured either way. I got that
> far, no further, but have done it as a combination and as singles. It
> just stops there.

Bear in mind that most references I've seen imply that putting two disks
on one IDE channel will bog things down enough to more than overcome any
advantage of striping (I haven't done that test, I regret to say, so I
don't know if it's true from personal experience).
	One thing I've never seen is a discussion of whether it matters if
one of those disks is unused: for example, hda1 is a hard drive and hda2
is one of the CDs, usually not even mounted. I would assume that safe, but
do not know for sure.

> 	Would setting the jumpers on the 4 drives to slave and master
> instead of cable select, go toward solving my problem?

I have never used or experimented with cable select, but have read that it
default cuts off dma transfers. Have you seen the program hdparm? If so,
once a cable-select disk is mounted, is it using dma?

> Would that  allow the boot process to continue?

There have been several references to boot failures due to cable select
issues, most notably in The Register's "Installing Linux" series. So I
would view it as a suspect.


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