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On Tue, Jun 21, 2005 at 12:06:11AM -0400, Allen Briggs wrote:
> OK.  Comparing the 'd_secperunit' field in the default label to that
> in the actual label read from the disk does work for me.=20

(you've already decided against this idea, but even so...)

This also strikes me as unlikely to work if the BIOS RAID is a pure
mirror of identical drives - won't the sizes be the same inside and
outside the ld/wd disklabel?

Or are these BIOS RAIDs actually using some space for a label/header
somewhere else on the disk that records configuration and state?
Clearly, they're not doing it at the start of the disk, or the
disklabels wouldn't collide.  If they're doing it somewhere else, does
the disklabel have to be adjusted to avoid that space?

Finally, each vendor might do their own thing WRT to where they store
config; some in BIOS nvram, some on the disk labels.  There's an AHCI
standard that some vendors follow (or only Intel?); what does it do?

Finally: The only immediate problem I can see with disabling (or
preempting) the component drives for findroot (by default, overridable
via hardwired config root) is if these BIOS RAID tools allow partial
or mixed RAID ld volumes on the one disk, rather than working only
with full physical units.  For example: a small mirrored root 'volume'
for booting and some other RAID level for the rest, or using the spare
space in a pair of mismatched-sized disks.  Again, probably this
varies by vendor.

While such things might seem best done with RAIDFrame under NetBSD, a
BIOS RAID config might be sharable between several OS's - or allow
BIOS booting from a small BIOS mirror before RF takes over for R5
data. =20

The common case would be for booting from a BIOS mirror, and thus it's
probably a sensible default; it might be nice if wdN were still
available as choices for 'boot -a' though, as well as tweakable with
kernel config.

--
Dan.
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