> On Jun 3, 2016, at 1:47 PM, Richard Elling <[email protected]> 
> wrote:
> 
> I agree with Jordan, mostly. However, there a way to know for sure…
> each label has a set of uberblocks. Use “zdb -lu” to see this information.
> If you can find a matching set of uberblocks for the right pool on enough 
> drives,
> then it is possible, though not guaranteed, that you can get enough of a pool
> to recover. OTOH, if the set does not include enough common uberblocks, then
> you know the end has come.

Thanks for the correction and follow-up, Richard.  Indeed, there might still be 
a faint shred of hope (though based on the pool topology he pasted, at least, 
very little I’d say, still - hope is hope!).

This also does kind of suggest that it might be in all of our mutual (ZFS-based 
technology vendor) interests to collaborate on a “ZFS data recovery FAQ”, just 
to pool our institutional knowledge on how to deal with the worst-case 
scenarios like this (assuming any kind of mitigation is possible at all) and 
perhaps improve the lives of all ZFS users in distress just a bit.  Checking 
The Google does suggest a paucity of such information.  This is the most Oracle 
appears to say, for example:  
http://docs.oracle.com/cd/E19253-01/819-5461/6n7ht6r0o/index.html 
<http://docs.oracle.com/cd/E19253-01/819-5461/6n7ht6r0o/index.html> along with 
this recent blog entry:  
https://blogs.oracle.com/zfs/entry/zfs_data_and_pool_recovery

Other snippets come from the FreeBSD and FreeNAS forums, since these appear to 
be “popular” mainstream deployments right now (at least in terms of # of google 
hits), but the advice is generally no better than “import, then try to import 
harder!”.

If no one else volunteers a location, I’d be happy to host the information at 
https://wiki.freenas.org <https://wiki.freenas.org/> - account creation and 
editing is open to the public.

- Jordan




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