zfs-fuse continues to be a superior recovery alternative to ZoL (Was: Fwd: "zfs rollback" hanged -- what to do?)

[Durval Menezes]

Hello Z-F folks, 

Cross-posting here in case anyone's interested.

Cheers, 

-- 

   Durval.

---------- Forwarded message ----------
Date: Sun, Dec 14, 2014 at 4:05 PM
Subject: Re: "zfs rollback" hanged -- what to do?
To: "zfs-d...@zfsonlinux.org" <zfs-d...@zfsonlinux.org>

Hello,

On Dec 14, 2014 1:10 PM, "Durval Menezes" <durval....@gmail.com> wrote:
> Just tried to rollback a snapshot here (EL6 clone with kernel 2.6.32-504.1.3.el6.x86_64 and ZFS  0.6.3-1.1 installed from the ZFS repo), and it never ends:
>
>> zfs rollback pool2014070601/main@20141119Z072639XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
>>
> Checked with "zpool iostat pool2014070601": exactly zero I/O for more than half an hour. 
>
> The process shows as "D" in ps, which AFAIK means it's blocked in uninterruptable wait for I/O.
>
> Any recommendations besides stopping whatever's possible to stop and then hard-resetting the machine?

No alternatives offered, so I proceeded as above and then imported the pool and tried to rollback again, with the same result: zfs rollback process in a neverending block at 'D' state. 

Hard reset again, but this time I moved the disk to another machine where I have zfs-fuse 0.7.0 installed: zfs-fuse imported the pool and processed the rollback with no issues, in much less time than I'm taking to type this. 

Seems zfs-fuse is still a very viable option for recovery, as long as one keeps his/her pools in a version zfs-fuse can handle (v26, I think). 

Crossposting to the zfs-fuse list on this, in case folks there are interested. 

Cheers,

-- 

   Durval.

[Gordan Bobic]

That means there is clearly a bug in ZoL that isn't in zfs-fuse. I don't suppose you happen to have gathered any data that might provide insight exactly where the bug might be?

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[Durval Menezes]

Hi Gordan, 

On Sun, Dec 14, 2014 at 4:11 PM, Gordan Bobic <gordan...@gmail.com> wrote:

That means there is clearly a bug in ZoL that isn't in zfs-fuse.

It would not have been the first. Pound for pound, ZoL is giving me much more headaches than zfs-fuse ever did. 

 

I don't suppose you happen to have gathered any data that might provide insight exactly where the bug might be?

No -- unfortunately, I'm in a hurry today: have a plane to catch in less than 2h from now, and I'm still packing up. 

But perhaps I can try to reproduce it later. 

Cheers, 

-- 

   Durval.