On Apr 30, 2019, at 11:17 PM, Michelle Sullivan <miche...@sorbs.net> wrote:
I have had it happen
several times over my IT career. If that happens to you the odds are
that it's absolutely unrecoverable and whatever gets corrupted is
*gone.*
Every drive corruption I have suffered in my career I have been able to
recover, all or partial data except where the hardware itself was totally
hosed (Ie clean room options only available)... even with brtfs.. yuk..
puck.. yuk.. oh what a mess that was... still get nightmares on that
one... but I still managed to get most of the data off... in fact I put
it onto this machine I currently have problems with.. so after the
nightmare of brtfs looks like zfs eventually nailed me.
It sounds from reading this thread that FreeBSD's built-in tools for ZFS
recovery were insufficient for the corruption your pool suffered. Have you
looked at the digital forensics realm to see whether those tools might help
you? This article claims to extend The Sleuth Kit to support pooled
storage such as ZFS, and they even describe recovering the bulk of an image
file from a pool that has a disk missing (Evaluation Section, "Scenario C:
reconstructing an incomplete pool"):
"Extending The Sleuth Kit and its underlying model for pooled storage file
system forensic analysis"
https://www.sciencedirect.com/science/article/pii/S1742287617301901
If said software has no tools to "walk" said
data or if it's impractical to have it do so you're at severe risk of
being hosed.
Umm what? I’m talking about a userland (libzfs) tool (Ie doesn’t need
the pool imported) such as zfs send (which requires the pool to be
imported - hence me not calling it a userland tool) to allow a sending of
data that can be found to other places where it can be either blindly
recovered (corruption might be present) or can be used to locate
files/paths etc that are known to be good (checksums match etc).. walk
the structures, feed the data elsewhere where it can be
examined/recovered... don’t alter it.... it’s a last resort tool when you
don’t have working backups..
See above.
BTW if you've never had a UFS volume unlink all the blocks within a file
on an fsck and then recover them back into the free list after a crash
you're a rare bird indeed. If you think a corrupt ZFS volume is fun try
to get your data back from said file after that happens.
Been there done that though with ext2 rather than UFS.. still got all my
data back... even though it was a nightmare..
Is that an implication that had all your data been on UFS (or ext2:) this
time around you would have got it all back? (I've got that impression
through this thread from things you've written.) That sort of makes it
sound like UFS is bulletproof to me.
There are levels of corruption. Maybe what you suffered would have taken
down UFS, too? I guess there's no way to know unless there's some way you
can recreate exactly the circumstances that took down your original system
(but this time your data on UFS). ;-)
Cheers,
Paul.
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