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Date:      Thu, 21 Oct 2010 19:32:46 +0200
From:      "Emil Smolenski" <ambsd@raisa.eu.org>
To:        "Matthew Seaman" <m.seaman@infracaninophile.co.uk>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: BIOS limitations on size of bootable zpool?
Message-ID:  <op.vkxscukzqvde5b@bolt.zol>
In-Reply-To: <4CC02B85.1050604@infracaninophile.co.uk>
References:  <4CC02B85.1050604@infracaninophile.co.uk>

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On Thu, 21 Oct 2010 14:01:09 +0200, Matthew Seaman  
<m.seaman@infracaninophile.co.uk> wrote:

> Dear all,
>
> I'm happy that gptzfsloader will work with just about any zpool
> configuration you could imagine, but...
>
> We have an HP DL185 G5 with a P400 raid array, fully populated with 12
> drives.  Since there's no JBOD mode (or at least, not one you can get to
> from the BIOS configuration screens), the array is configured as 12
> single disk RAID0 arrays.   As I posted about previously, we had FreeBSD
> 8.1-STABLE installed on a 6 disk raidz1, and everything was happy.
> However, we were having some difficulty adding a second vdev -- another
> raidz1 using the other 6 drives.
>
> Well, to cut a long story short: eventually we did this by hot-plugging
> disks 7 -- 12 after FreeBSD was up and running.  Everything was cool and
> dandy, and we had the server running on all drives after setting up gpt
> partition tables and doing a 'zpool add'.
>
> Until we tested rebooting.
>
> On attempted reboot, the loader reported 8 drives, and subsequently ZFS
> flailed with the dreaded "ZFS: i/o error - all block copies unavailable"
> error.  Now, we've had a poke through FreeBSD sources, and as far as we
> can tell, FreeBSD will work with up to 31 devices being reported from
> the BIOS.  Is this correct, and the limitation is in what the hardware
> is reporting to the loader at the early stages of booting?
>
> Any good tricks for getting round this sort of limitation?  Our current
> plan is to set up a USB memstick with /boot on it, by adapting the
> instructions here: http://wiki.freebsd.org/RootOnZFS/UFSBoot -- which
> isn't ideal as the memstick will be a single point of failure.

  I think I've encountered the same problem as you. In my configuration  
there is also HP server with HP SmartArray with six disks configured as  
single disk RAID0 logical units. I don't think it is related to size of  
the pool (try to test with small GPT partitions -- for me it also doesn't  
work). I think it is something with this specific hardware and ZFS. I will  
provide more details soon, but for know could you test following  
configurations:
- mirror (it works for me),
- raidz(2) (it doesn't work for me),
- raidz(2) but without SmartArray controller -- adX or adaX disks (it  
works for me).

Please try 'status' command while seeing "ZFS: i/o error..." message.

-- 
am



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