[arch-general] btrfs & Arch

[C Anthony Risinger]

On Thu, Aug 25, 2011 at 2:19 AM, Gour-Gadadhara Dasa <gour at atmarama.net> wrote:
> On Wed, 24 Aug 2011 12:44:10 -0500
> C Anthony Risinger <anthony at xtfx.me> wrote:
>
>> unfortunately you can only do /boot on btrfs if you use a single disk
>> due to bootloader limitations:
>
> Is it only bootloader limitation considering that wiki page says: "This setup
> does not support btrfs RAID because a separate boot partition/device is needed,
> ie. only one drive allowed. Pending releases of mkinitcpio-btrfs will attempt
> to provide solutions." ?

im not sure im understanding correctly ... mkinitcpio-btrfs is just an
initcpio hook performing a handful of trixy things to "rollback in
time", ie. boot an older snapshot.  everything it does is orthogonal
to the /boot problem ... though i had some experimentations using a
two-stage system that booted a minimal kernel far enough to load the
real kernel off the btrfs array -- along with other activity this
could "enable" /boot on a btrfs array -- not even tested yet though.

fundamentally syslinux and friends (AFAIK) are not capable of reading
a disk if part of an array.  syslinux can't even look inside a
subvolume ... hence kernel rollbacks are not straightforward.

you *can* however have / on btrfs, *and* an array ... so long as your
/boot is still using `md` + <other FS>.  maybe btrfs could even be
that FS ... not sure.  for this to work you just need the `btrfs` hook
included with Arch, or you need to pass all the devices in the array
as a mount option (eg. via `rootflags` on kernel bootline)

-- 

C Anthony