[syslinux] multi-device btrfs volumes

[H. Peter Anvin]

On 12/18/2013 08:50 AM, Gene Czarcinski wrote:
> Currently, extlinux does not support multi-device BTRFS volumes.  Is
> anything planned to add this support?  I believe I understand that it
> has to be a lot more complicated with multi-devices because you are
> doing the device I/O at a very low level.
> 
> However, grub2 does support booting from multi-device BTRFS volumes
> (actually subvolumes on multi-device BTRFS volumes).  I cannot be
> impossible or is this one of those "just too hard to be worth the
> effort" situations?
> 
> Gene

Grub2 is a bit, ahem, cavalier about the way it handles multidevice
support, that can lead to unnecessary boot failures.  Unfortunately the
way btrfs handles RAID-1 is nonstandard and problematic for more than
two drives (it takes RAID-1 to mean "any two drives" rather than "all
drives".)  It is possible with some of the recent multidevice support
patches, but there is a huge pit of "let's repeat Grub2's design
mistakes" here...

	-hpa