Re: Can't replace a faulty disk of raid1

["Lluís Batlle i Rossell" <viric@viric.name>]

On Fri, Oct 26, 2012 at 12:57:21PM +0200, Lluís Batlle i Rossell wrote:
> I had a raid1 btrfs (540GB) on vanilla 3.6.3, a disk failed, and removed it at
> power off, plugged in a new one, partitioned it (to 110GB, by error), and added
> it to btrfs.
> 
> I tried to remove the missing device, and it said "Input/output error" after a
> while. Next attempts simply gave "Invalid argument".
> 
> Some data:
> 
> # btrfs fi df /
> Data, RAID1: total=507.62GB, used=417.08GB
> Data: total=25.32GB, used=22.48GB
> System, RAID1: total=32.00MB, used=92.00KB
> System: total=4.00MB, used=0.00
> Metadata, RAID1: total=19.97GB, used=5.50GB

For the sake of mail archiving and future searches, problem solved; there is
some 'single' data there (22.48GB). Removing the files containing that data
allowed "btrfs device delete missing /" to work.

For what I know, at 3.6 there were no error messages indicating about that.
Then, scrub does not check anything related to missing disks, so it reports that
all works. And I think that btrfsck also does not report anything related to
missing disks.

The way to get what files had the missing data was to run "tar c /", and wait
for the errors report on EIO. Then I removed those files.

Thanks a lot to Josef, who sent me patches adding error reports, to get closer
to the source the errors, and the rest of the helpful people at the #btrfs @
freenode

Regards,
Lluís.