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Date:      Mon, 29 Oct 2012 09:34:46 -0500
From:      Chuck Burns <break19@gmail.com>
To:        freebsd-fs@freebsd.org
Subject:   Re: graid often resyncs raid1 array after clean reboot/shutdown
Message-ID:  <508E9406.5040408@gmail.com>
In-Reply-To: <508E91CF.5070003@FreeBSD.org>
References:  <508E0C3F.8080602@freebsd.org> <508E3E81.9010209@FreeBSD.org> <508E49AD.4090501@FreeBSD.org> <508E91CF.5070003@FreeBSD.org>

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On 10/29/2012 9:25 AM, Alexander Motin wrote:
> On 29.10.2012 11:17, Alexander Motin wrote:
>> On 29.10.2012 10:29, Alexander Motin wrote:
>>> Hi.
>>>
>>> On 29.10.2012 06:55, Lawrence Stewart wrote:
>>>> I have a fairly new HP Compaq 8200 Elite desktop PC with 2 x 1TB
>>>> Seagate
>>>> ST1000DM003 HDDs in raid1 using the on-board Intel Matrix RAID
>>>> controller. The system is configured to boot from ZFS off the raid1
>>>> array, and I use it as a KDE GUI (with on-cpu GPU + KMS) desktop.
>>>>
>>>> Everything works great, except that after a "shutdown -r now" of the
>>>> system, graid almost always (I believe I've noted a few times where
>>>> everything comes up fine) detects one of the disks in the array as
>>>> stale
>>>> and does a full resync of the array over the course of a few hours.
>>>> Here's an example of what I see when starting up:
>>>
>>>  From log messages it indeed looks like result of unclean shutdown. I've
>>> never seen such problem with UFS, but I never tested graid with ZFS. I
>>> guess there may be some difference in shutdown process that makes RAID
>>> metadata to have dirty flag on reboot. I'll try to reproduce it now.
>>
>> I confirm the problem. Seems it happens only when using ZFS as root file
>> system. Probably ZFS issues some last moment write that makes volume
>> dirty. I will trace it more.
>
> I've found problem in the fact that ZFS seems doesn't close devices on
> shutdown. That doesn't allow graid to shutdown gracefully. r242314 in
> HEAD fixes that by more aggressively marking volumes clean on shutdown.
>
See, the thing is, ZFS was designed to accomplish the same thing that 
graid does... It's -designed- to be run directly on bare drives. Perhaps 
this isn't really a bug in ZFS, but is more of a consequence of doing 
something that isn't supported: ie: running zfs on top of graid.

Chuck

-- 
Chuck Burns <break19@gmail.com>



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