Help Recovering FBSD 8 ZFS System

Drew Tomlinson drew at
Mon Jan 2 22:15:31 UTC 2012

On 1/2/2012 12:36 PM, Daniel Staal wrote:
> --As of December 31, 2011 1:40:59 PM -0800, Drew Tomlinson is alleged 
> to have said:
>> Thus it appears I am missing ad16 that I used to have.  My data zpool 
>> was
>> the bulk of my system with over 600 gig of files and things I'd like to
>> have back.  I thought that by creating a raidz1 I could avoid having to
>> back up the huge drive and avoid this grief.  However it appears I have
>> lost 2 disks at the same time.  :(
>> Any thoughts before I just give up on recovering my data pool?
> Ouch.  All I can really say is 'Redundancy is not backup', but that's 
> a bit trite...

Yes, I know redundancy doesn't protect against operator error and thus 
isn't a true backup.  However this is a personal system whose main 
function was to store DVDs, MP3s, photos, and the like.  I can recreate 
most of the content and have backups of the photos up until about a year 
ago (bad me).

> The one thing you haven't mentioned trying that might be worth the 
> attempt is trying the recovery from a 9.0 disk.  There has been work 
> done on the ZFS system, and it's possible that something might work.   
> But that's mostly just to be thorough...

I may try this.  However I suspect before anything can work, I have to 
get the missing disk(s) detected by the OS.  One (ad6) is detected but 
full of errors.  There is another that's not even seen.

> As for what it was telling you: It was just saying it couldn't open 
> the drives.  ;)  Which does bring up one other option: If you've got a 
> different drive controller, you might try plugging the drives into 
> it.  (In the hopes that it's the *controller* and not the drive that's 
> gone bad. Unlikely, bit it *does* happen.)

Thanks.  I'll keep that in mind.  However in this case, the controller 
is a SATA that's integrated into the motherboard.  Since two of 4 are 
working, that would mean the controller is OK, right?  I guess I could 
swap SATA cables for a test.

> (Depending on the value of the data pool, a good data recovery service 
> might be able to do something as well.  But they'd have to be a very 
> good service, and know what they were working with.)
>> And regarding my root pool, my system can't mount root and start.  What
>> do I need to do to boot from my degraded root pool.  Here's the current
>> status:
>> # zpool status
>>    pool: root
>>   state: DEGRADED
>> status: One or more devices could not be opened.  Sufficient replicas
>> exist for
>>          the pool to continue functioning in a degraded state.
>> action: Attach the missing device and online it using 'zpool online'.
>>     see:
>>   scrub: none requested
>> config:
>>          NAME                                            STATE     READ
>>          root                                            DEGRADED     0
>> 0     0
>>            mirror                                        DEGRADED     0
>> 0     0
>>              gptid/5b623854-6c46-11de-ae82-001b21361de7  ONLINE       0
>> 0     0
>>              12032653780322685599                        UNAVAIL      0
>> 0     0  was /dev/ad6p3
>> Do I just need to do a 'zpool detach root /dev/ad6p3' to remove it from
>> the pool and get it to boot?  And then once I replace the disk a 'zpool
>> attach root <new partition>' to fix?
>> Thanks for your time.
> Personally, I'd do a 'zpool replace /dev/ad6p3 /dev/$NEWDRIVE', but 
> the above should work as well.  What's odd though is that you can't 
> boot from it as is: Degraded should be considered functional, and it 
> should let you boot.  You mentioned updating the zpool to v15.  Did 
> you update the boot block at the same time?  (Just checking the 
> basics.)  It'd need to be able to read the updated zpool.

I assume I upgraded the boot block since I've had no trouble booting 
before the drive failures and the upgrade was a long time ago.

Thanks for your help.


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