Re: Debian Bullseye install btrfs raid1

[Nikolay Borisov <nborisov@suse.com>]

On 4.05.22 г. 13:02 ч., richard lucassen wrote:
> On Wed, 4 May 2022 12:27:29 +0300
> Nikolay Borisov <nborisov@suse.com> wrote:
> 
>>> Question: is this newbie trying to set up an impossible config or
>>> have I missed something crucial somewhere?
>>
>> That's the default behavior, the reasoning is if you are missing one
>> device of a raid1 your data is at-risk in case the 2nd device fails.
>> You can override this behavior by mounting in degraded mode, that is
>> mount -odegraded
> 
> Another thing: sda3/sdb3 is the root fs, so I need to tell grub that
> it's ok to mount a degraded array (one or another way, don't know
> if it's possible, I'm not a grub guru). Adding it to fstab makes
> no sense as there is no fstab at that time.
> 
> OTOH, when using md devices, the / fs is mounted as Degraded Array and
> the remaining device remembers that this had happened. If the second
> disk is replaced I have to add it manually using mdadm. The first disk
> is "master". Using md the system boots and mounts / and thus all tools
> are available to repair the array.
> 
> The wiki explains how to repair an array, but when the array is the
> root fs you will have a problem.
> 
> So, what should I do when the / fs is degraded?

In case of btrfs raid1 if you managed to mount the array degraded it's 
possible to add another device to the array and then run a balance 
operation so that you end up with 2 copies of your data. I.e I don't see 
a problem? Have I misunderstood you?
> 
> R.
>