Snapshots that won't delete [was: Re: ZFS on root booting...]

[Andriy Gapon]

On 12/09/2014 08:12, Shane Ambler wrote:
> On 11/09/2014 16:42, Ben Morrow wrote:
>> Quoth Adam McDougall <mcdouga9 at egr.msu.edu>:
>>>
>>> Were you running a newer kernel with an older format zpool?  I heard
>>> ixsystems had customers doing that and ran into corruption when they
>>> tried to modify the zpool in some way (expand? I don't remember).
>>> http://www.bsdnow.tv/episodes/2014_07_09-zfs_war_stories
>>
>> Oh! Might this be what's causing a problem I've been meaning to ask
>> about?
>>
>> My desktop at home is running (a patched, but not anywhere to do with
>> ZFS) 10-STABLE from a while ago, with a zpool that was created under
>> 8.2-R and is still at version 15. I have been deliberately not upgrading
>> it, because I saw no reason to and it seemed safer to leave things as
>> they were.
>>
>> Recently, though, my dump script has started having occasional problems
>> with snapshots that won't delete. Pending further investigation I have
>> been renaming them to allow the recursive delete to succeed, and (so
>> far) rebooting has always made it possible to get rid of them. 
> 
> I have seen that issue with 9.2 and at least one other person mentioned
> it as well. I currently have a snapshot that I accessed at least 3 weeks
> ago and renamed to keep rotations working and have not accessed since,
> it still won't delete as it is busy. I can only delete these snapshots
> after a reboot.
> 
> The only cause I know is accessing the snapshot.
> I can simply ls .zfs/snapshot/daily.01/somefolder to prevent it being
> deleted. With a manual zfs destroy I get "dataset is busy" and have not
> found a way to find any process that has hold of it.

Look for it in `mount` output.

> It seems that some aging of the snapshot needs to happen. Testing a
> rotate, access, rotate keeps working ok, but access last nights
> snapshot and then rotate and it blocks.
> 
> I'm fairly sure that I was running 9.1 when I created this zpool and
> then later upgraded to 9.2. zpool upgrade says "This system supports
> ZFS pool feature flags" and "Pool 'zrpleader' already has all supported
> features enabled".
> 


-- 
Andriy Gapon