Re: Error: Failed to read chunk root, fs destroyed

[Lionel Bouton <lionel-subscription@bouton.name>]

Hi,

Le 23/07/2020 à 23:51, Davide Palma a écrit :
> Dear Lionel,
>
> > I probably won't be able to help but while this is fresh in your memory
> > please try to remember the exact sequence.
>
> I wish I could give you the .bash_history file,  but the sequence is
> the one I wrote. I tried running many balances before the ramdisk
> stuff by starting with -musage=0 and -dusage=0 and got to about 30
> before it started looping, I don't think this is useful but now you
> have 100% of my memory :)
>
> > If that's indeed the case, removing the loop device later on will indeed
> > break the filesystem as several metadata block groups will be entirely
> > missing (dup will probably have allocated the two duplicates on the loop
> > block device where space was available).
>
> Doesn't this defeat the whole point of raid1?

My point is that I saw nothing that pointed to raid1 being used on your
filesystem in the list of steps you described. I understand it was your
intent to use raid1 (although it isn't clear why as you didn't provide a
link for the advice you were following) but I'm not sure you actually did.

Simply adding a device to a BTRFS filesystem doesn't convert your
filesystem block groups it only adds usable space. You'd need to use a
balance command for converting the block groups to raid1.
Something like :
btrfs balance start -mconvert=raid1 -dconvert=raid1 <yourfs>

Best regards,

Lionel