[ale] initramfs capable of a multi-device btrfs / new initramfs with dracut help?

[Pat Regan]

On Mon, 19 Jul 2010 00:32:40 -0400
"Michael B. Trausch" <mike at trausch.us> wrote:

> but I am pretty sure it was the OS/2 bootloader program) that had as a
> requirement a dedicated partition just for it.  I think that the ideal
> bootloader would keep this requirement.  You could then afford to
> have a slightly larger bootloader that understood things like the
> types of software RAID used by various operating systems such as
> Linux and the BSD family of operating systems, and be able to boot
> from them all without a terribly large amount of effort.

How is putting the bootloader on a separate partition significantly
different than putting the kernel and initrd on a separate partition?  

> This would make it possible to do something like have a read-only SD
> card or similar flash device contain the bootloader (or, for that
> matter, for the bootloader to be placed in a decently sized firmware).
> It could afford to understand a wide variety of filesystems and
> storage formats, including LVM2, BSD disklabels, and the various
> types of software RAID used by different operating systems.

Then it becomes a single point of failure.  I'd rather have my
bootloader on all my drives and my kernel and initrd on a raid 1, like
we already do.

I've always been one to champion the durability of flash but I had to
RMA my X25-m twice in the first 6 months.

> Anyway, this particular email has gotten to be far too long, so I'll
> end it now... later!

I'll take this as my turn to voice my complaint about software raid...

I'm never certain what is going to happen when a disk dies, especially
if it is the first disk.  Is the drive dead enough that the BIOS is
going to skip it during the boot process?  Is it alive enough that the
BIOS might try to boot it?

If I'm using software raid it is very likely to be in a lower end
machine.  It probably doesn't have swappable drive cages, so I'm going
to have to bring it down to replace that boot drive.  If I put a blank
drive in there is the BIOS going to tell me no OS found?  It will
likely depend on the machine...

I only mention this because I've been thinking about it today.  I'm
planning to drive out to replace the boot drive in a colocated machine
of mine.  I saved a few bucks buying a server with no hot swap cages.
If I could hot swap, I could just pop the drive in an reload grub.

I'm being paranoid, I dd-ed down a copy of the drive up to the end of
the /boot partition and dd-ed it onto the replacement drive.  :)

Pat