partial Dead disk, corrupted backup tapes, bah
2007-12-25 11:17:00
While not resolved yet, figured I'd at least take a moment to thank the
list members for all the helpful and supportive advice. I got a *lot* of
replies (too many people to list, really) within the first couple of hours.
Lots of suggestions about data services (Ontrack www.ontrack.com and Ibas
www.ibas.no being the two most recommended), and some ideas about
manipulating the tapes to try and read the damaged data. (A trick about
powering off the drive while writing over the EOM mark, then trying to
recover from that. You can find that in the sun-managers archives at
latech.)
I ended up today deciding not to mucky-muck around with the tapes any more
(tried spacing past the end, back and forth, nothing involving a write) in
case I screwed them up so bad that a recovery service couldn't do anything
with them, and packed the drive and the tapes off to a Canadian firm
(www.datarec.com), in the interests of time and avoiding the long delays of
interational customs from my part of the world (yes, the USA counts as
international, I'm in Canada. Sigh).
I'll clarify a couple of points some folks noticed. I don't keep multiple
slices on one tape, when I said "whole disk" I probably should have said
"whole slice" since I only have one slice on this particular disk (where
/export/home was being kept, other partitions like the os stuff are on
other disks). By "previous dump" I meant the dump from the last time this
tape was put through the rotation that was (to be) overwritten by this
dump, so it's not as easy as just spacing to the end of one dump and
reading another. I've been doing level 0 dumps every time, since I don't
have that many disks overall, and incrementals always scare the dickens out
of me.
Among the advice I got (and I agree with) was to use more tapes in the
rotation. Two tapes doesn't cut it, especially in cases like this. For
what I'll pay for the recovery I could have bought lots and lots of tapes.
Another idea was with disks being as cheap as they are these days to get
another drive, and "backup" the disk by mirroring over to it (either with
disksuite, which I don't use, or cron it to mount/mirror/unmount on my
own), in addition to the tapes. That has the advantage that I'd actually
be able to *work* on the data even with the primary disk gone.
And... no matter how bad things seem to you, as I found, there were people
who had even worse stories of backups and disks gone awry. Doesn't really
help me, but keeps you from feeling alone :)
Anyway, sorry if this has gotten too long again. Hopefully tomorrow the
data place will have some good (but unfortunately expensive) news for me.
Best regards,
Steven Cogswell (cogswell@nbnet.nb.ca)
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