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Date:      Fri, 12 Sep 2014 14:42:56 +0930
From:      Shane Ambler <FreeBSD@ShaneWare.Biz>
To:        freebsd-stable@freebsd.org
Subject:   Re: Snapshots that won't delete [was: Re: ZFS on root booting...]
Message-ID:  <541280D8.9090500@ShaneWare.Biz>
In-Reply-To: <20140911071233.GA50585@anubis.morrow.me.uk>
References:  <FE64613E-B083-436C-8A08-13923ED88797@icloud.com> <7F008C560B48412AB66A1EBD9382DDAE@multiplay.co.uk> <CC276D59-F83C-4C78-BD9B-84040D3DE3E4@icloud.com> <9315C209-701A-49EF-85D3-ACCCD1513EC3@icloud.com> <959C54D2C8EB4AC8983DC1DA3CE042E3@multiplay.co.uk> <9F24DD48FBEA46C39F98DF600D46DA1A@multiplay.co.uk> <B4A16726-142D-458A-9B3A-153BDD579A63@icloud.com> <BAB9F50F-9D2C-435C-8035-659E2B412FC7@icloud.com> <4450778127F4407EB6566A0FE11CD651@multiplay.co.uk> <090135D4-8B1F-42B4-82FC-6FD2F1DBDDA8@icloud.com> <20140911071233.GA50585@anubis.morrow.me.uk>

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On 11/09/2014 16:42, Ben Morrow wrote:
> Quoth Adam McDougall <mcdouga9@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.

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".

-- 
FreeBSD - the place to B...Serving Data

Shane Ambler




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