Re: Raid1 won't mount degraded

[Subscription Account <4subsacct+btrfs@gmail.com>]

On Sun, Jan 29, 2017 at 8:49 PM, Adam Borowski <kilobyte@angband.pl> wrote:
> On Sun, Jan 29, 2017 at 08:26:54PM -0500, Subscription Account wrote:
>> On Sun, Jan 29, 2017 at 3:16 PM, Adam Borowski <kilobyte@angband.pl> wrote:
>> > On Sun, Jan 29, 2017 at 08:12:56AM -0500, Subscription Account wrote:
>> >> [ 2506.816795] BTRFS: missing devices(1) exceeds the limit(0),
>> >> writeable mount is not allowed
>> >>
>> >> In the read-only mode I am not able to add a new device or replace :(.
>> >> Please help.
>> >
>> > A known problem; you can mount rw degraded only once, if you don't fix the
>> > degradation somehow (by adding a device or converting down), you can't mount
>> > rw again.
>>
>> Uh oh! I wish I know that I only had one shot :(.
>
> No data is actually lost, it was raid1, it's raid1+single now.  The mount
> check is naive and in this case wrong.
>
>> > If you know how to build a kernel, here's a crude patch.
>>
>> I am feeling a little lucky because I still have the other disk and I
>> am assuming if I remove my current disk and put the other disk in, I
>> would be able to mount it once again?
>
> Not sure if that's a good idea if the copies are out of sync.
>

Not sure I follow, since I will be removing the current disk which may
have some changes, but I don't really care for those changes. When I
put the other disk in, I would be removing the first one so there is
only one disk at one time, it is just that I will go back to a few
days ago status? Am I missing something here?

Thanks,

--
Raj

>> Also, since I have couple times already tried btrfs repair etc, can I
>> trust the current disk anyways?
>>
>> if I get into issue again, I would definitely use the patch to
>> recompile the kernel and thanks a lot for the same.
>
> No, the patch doesn't prevent the issue.  It lets you recover -- ie, it
> should help in the situation you're in right now.
>
>
> Meow!
> --
> Autotools hint: to do a zx-spectrum build on a pdp11 host, type:
>   ./configure --host=zx-spectrum --build=pdp11