RAID tail of woe :(

[Anders Karlsson]

On Mon, 2006-05-01 at 16:58 +0100, Dave S wrote:
[snip]
> I am sorry if I was not clear.
> 
> In a nutshell I have Parallel ATA HDD on hda and hdc directly of off my 
> motherboard running software raid 1 - it works like a dream and I am very 
> happy with it.

Could you clarify if this is fakeraid or if this is the MD RAID system
in the kernel.

Whether fakeraid or MD, a hardware RAID controller will not help you
read your current RAID setup in any faster or safer manner than a plain
IDE controller.

> However I have a CDROM and a DVDRW drive on hdb and hdd sharing the hda and 
> hdc controllers. Because they cripple my system when I am reading or burning 
> dvds I want to move them to another IDE controller, ie via a PCI card.

One of the problems with PATA (and SATA wisely avoided this problem) is
that while in theoryy, you can have two devices attached to one cable,
in practice it seldom works well. The guideline is that on one chain,
you only put devices that are the same, i.e. same bus speed, DMA mode
and type. Mixing a DVD writer (usually runs in UDMA2 mode) with a HDD
(usually runs in UDMA5 mode) will cause issues.

> Unfortunately it seems my PCI Parallel ATA card cannot detect or boot CDROM or 
> DVDRW drives attached to it.

This may just be a BIOS setting on your PC. You may have to allow
booting of off-board controllers. It *may* also be worth updating BIOS
and firmware to latest levels.

What you also could do, if you are running MD, is hang a disk as master
on the primary chain on the motherboard and on the PCI adapter (hda and
hde), then hang the DVD drives as masters on the secondary chains on the
on-board and PCI controllers (hdc and hdg). That should work, allowing
you to boot both disks and optical media. This solution will *not* work
if you are using fakeraid.

> Hope this clarifies things :)

HTH,

-- 
Anders Karlsson <trudheim at gmail.com>
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