On Feb 14, 2013, at 7:44 AM, Martin Steigerwald <mar...@lichtvoll.de> wrote:

> For some reason BTRFS is still trying to write to /dev/sdd, which isn“t
> there anymore. That perfectly explains those lost page writes for me. If
> that is the case, this seems to me like a serious bug in BTRFS.

Following the ICRC ABRT error, /dev/sdd becomes /dev/sdi. Btrfs-progs 
recognizes this by only listing /dev/sdi and /dev/sde as devices in the volume. 
But the btrfs kernel space code continues to try to write to /dev/sdd, while 
/dev/sdi isn't getting any writes (at least, it's not filling up with data).

Btrfs kernel space code is apparently unaware that /dev/sdd is gone. That seems 
to be the primary problem.

A question is, if the kernel space code was aware of a member device vanishing 
and then reappearing, whether as the same or different block device 
designation, should it automatically re-add the device to the volume? Upon 
being re-added, it would be out of sync, leading to a follow-up question about 
whether it should be auto-scrubbed to fix this? And yet another follow-up 
question which is if the file system metadata contains information that can be 
used similar to the function of the md write-intent bitmap, reducing the time 
to catch the drive up, avoiding a full scrub?


Chris Murphy--
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