Hi,
I have followed the progress made in the btrfs filesystem over time and
while I have experimented with it a little in a VM, I have not yet used
it in a production machine.
While the lack of a complete fsck was a major issue (I read the update
that the first working version is about to be released) I am still
worried about an issue I see popping up.
How is it possible that a copy-on-write filesystem becomes corrupted if
a power failure occurs? I assume this means that even (hard) resetting a
computer can result in a corrupt filesystem.
I thought the idea of COW was that whatever happens, you can always
mount in a semi-consistent state?
As far as I can see, you wind up with this:
- No outstanding writes when power down
- File write complete, tree structure is updated. Since everything is
hashed and duplicated, unless the update propagates to the highest
level, the write will simply disappear upon failure. While this might be
rectified with a fsck, there should be no problems mounting the
filesystem (read-only if need be)
- Writes are not completed on all disks/partitions at the same time. The
checksums will detect these errors and once again, the write disappears
unless it is salvaged by a fsck.
Am I missing something? How come there seem to be plenty people with a
corrupt btrfs after a power failure? And why haven't I experienced
similar issues where a filesystem becomes unmountable with say NTFS or
Ext3/4?
--
Regards,
Berend Dekens
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