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Date:      Thu, 03 Mar 2011 13:51:47 +0100
From:      Alexander Leidinger <Alexander@Leidinger.net>
To:        Fabian Keil <freebsd-listen@fabiankeil.de>
Cc:        freebsd-fs@FreeBSD.org, Pawel, freebsd-current@FreeBSD.org, Dawidek <pjd@FreeBSD.org>
Subject:   Re: HEADS UP: ZFSv28 is in!
Message-ID:  <20110303135147.20096fpe1ntz75k8@webmail.leidinger.net>
In-Reply-To: <20110303130130.29a066a1@r500.local>
References:  <20110227202957.GD1992@garage.freebsd.pl> <20110228192129.119cac0c@r500.local> <20110228214847.0000078c@unknown> <20110303130130.29a066a1@r500.local>

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Quoting Fabian Keil <freebsd-listen@fabiankeil.de> (from Thu, 3 Mar  
2011 13:01:30 +0100):

> Alexander Leidinger <Alexander@Leidinger.net> wrote:
>
>> On Mon, 28 Feb 2011 19:21:29 +0100 Fabian Keil
>> <freebsd-listen@fabiankeil.de> wrote:
>>
>> > Pawel Jakub Dawidek <pjd@FreeBSD.org> wrote:
>> >
>> > > I just committed ZFSv28 to HEAD.
>> >
>> > I updated the system without removing the tuning for ZFSv15
>> > first, and somehow this completely messed up the performance.
>> > Booting the system took more than ten minutes and even once
>> > it was up it was next to unresponsive.
>> >
>> > I'm not sure which sysctl was to blame, but after removing
>> > all but vfs.zfs.arc_max="800M" and rebooting, the problem
>> > was gone.
>>
>> When you add the tuning back, does it take minutes again to boot? If
>> not, I assume it was cleaning up some leftovers the old version was not
>> able to cleanup.
>
> I haven't tried that yet, but as I didn't upgrade the system's
> storage pool I don't think ZFS is supposed to do any such clean-ups.

AFAIK the new code knows how to remove some superfluous parts in your  
pool (no matter at which version the pool is), which the old code just  
skipped over. Such leftovers may not be in all pools, they show up  
just in some use cases. For this reason I asked to verify by adding  
the tuning back to this system (if possible).

If it is not a production-like system which does not accept downtime,  
this verification consumes less resources than sending out a developer  
hunting for a problem which may not even exist.

Bye,
Alexander.

-- 
A short cut is the longest distance between two points.

http://www.Leidinger.net    Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org       netchild @ FreeBSD.org  : PGP ID = 72077137



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