To recap for those who don't recall my plaintive cries for help, I lost a pool
due to the following sequence of events:
- One drive in my raidz array becomes flaky, has frequent "stuck" I/Os due to
drive error recovery, trashing performance
- I take flaky drive offline (zpool offline...)
- I bring down the server and swap out the disk
- When the server comes back up, the pool won't import, because a _different_
drive has decided to not spin up
- I swap the "flaky" disk back in
- Pool won't import because the "flaky" disk is several TxGs behind (and, if I
boot into a boot CD, because it's "offline")
Victor Latushkin from Sun's Moscow office once again comes to the rescue,
rolling back the uberblocks to a (mostly) sane TxG ID, and providing new zfs
bits with a read-only import option (to make sure I didn't trash things worse
than they already were...)
I have finally completed recovery of my 3+ TB of data. I lost one email account,
about 10 non-spam non-trash emails from my email account, and one ISO image. I'm
fairly certain that rolling back another few TxGs would have gotten the lost
email account directory back, but as the user had a complete offline copy on his
desktop, it wasn't worth it. I suspect the emails that were not recoverable from
my account were actually ones I had recently deleted / filed as spam, but I
can't be certain (I know the file names, but 1013456. isn't very descriptive...)
If I had been using any other file system, I would have lost everything. I had
partial backups of my most critical data, but the loss would have been extremely
painful. Due to the design of ZFS and the help from Victor (hopefully soon to no
longer be needed with delivery of the zpool rollback tool(s)), not only did I
recover the vast majority of my data, I know what I didn't recover, and I know
that what I did recover is not corrupt.
Thanks, ZFS! I am _so_ glad I became an early adopter many years ago when I
built this home server.
For the record, my new, larger pool is raidz2, and I am plugging the holes in my
offsite backup syncs to cover more of my data (not all of it, as 8+ TB of data
is a lot... I will probably purchase some big, slow disks next year to allow me
to keep a full offline backup locally).
--
Carson
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