Re: BTRFS with RAID1 cannot boot when removing drive

[Saint Germain <saintger@gmail.com>]

Hello !

On Mon, 10 Feb 2014 19:18:22 -0700, Chris Murphy
<lists@colorremedies.com> wrote :

> 
> On Feb 9, 2014, at 2:40 PM, Saint Germain <saintger@gmail.com> wrote:
> > 
> > Then I added another drive for a RAID1 configuration (with btrfs
> > balance) and I installed grub on the second hard drive with
> > "grub-install /dev/sdb".
> 
> That can't work on UEFI. UEFI firmware effectively requires a GPT
> partition map and something to serve as an EFI System partition on
> all bootable drives.
> 
> Second there's a difference between UEFI with and without secure boot.
> 
> With secure boot you need to copy the files your distro installer
> puts on the target drive EFI System partition to each addition
> drive's ESP if you want multibooting to work in case of disk failure.
> The grub on each ESP likely looks on only its own ESP for a grub.cfg.
> So that then means having to sync grub.cfg's among each disk used for
> booting. A way around this is to create a single grub.cfg that merely
> forwards to the "true" grub.cfg. And you can copy this forward-only
> grub.cfg to each ESP. That way the ESP's never need updating or
> syncing again.
> 
> Without secure boot, you must umount /boot/efi and mount the ESP for
> each bootable disk is turn, and then merely run:
> 
> grub-install
> 
> That will cause a core.img to be created for that particular ESP, and
> it will point to the usual grub.cfg location at /boot/grub.
> 

Ok I need to really understand how my motherboard works (new Z87E-ITX).
It is written "64Mb AMI UEFI Legal BIOS", so I thought it was really
UEFI.

> 
> > 
> > If I boot on sdb, it takes sda1 as the root filesystem
> > If I switched the cable, it always take the first hard drive as the
> > root filesystem (now sdb)
> > If I disconnect /dev/sda, the system doesn't boot with a message
> > saying that it hasn't found the UUID:
> > 
> > Scanning for BTRFS filesystems...
> > mount:
> > mounting /dev/disk/by-uuid/c64fca2a-5700-4cca-abac-3a61f2f7486c
> > on /root failed: Invalid argument
> 
> Well if /dev/sda is missing, and you have an unpartitioned /dev/sdb I
> don't even know how you're getting this far, and it seems like the
> UEFI computer might actually be booting in CSM-BIOS mode which
> presents a conventional BIOS to the operating system. Disintguishing
> such things gets messy quickly.
> 

/dev/sdb has the same partition as /dev/sda.
Duncan gave me the hint with degraded mode and I managed to boot
(however I had some problem with mounting sda2).

> > 
> > Can you tell me what I have done incorrectly ?
> > Is it because of UEFI ? If yes I haven't understood how I can
> > correct it in a simple way.
> > 
> > As extra question, I don't see also how I can configure the system
> > to get the correct swap in case of disk failure. Should I force
> > both swap partition to have the same UUID ?
> 
> If you're really expecting to create a system that can accept a disk
> failure and continue to work, I don't see how it can depend on swap
> partitions. It's fine to create them, but just realize if they're
> actually being used and the underlying physical device dies, the
> kernel isn't going to like it.
> 
> A possible work around is using an md raid1 partition as swap.
> 

I understand. Normally the swap will only be used for hibernating. I
don't expect to use it except perhaps in some extreme case.

Thanks for your help !