From owner-freebsd-fs@FreeBSD.ORG  Wed Nov 18 13:51:00 2009
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From: Robert Noland <rnoland@FreeBSD.org>
To: Emil Smolenski <ambsd@raisa.eu.org>
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Date: Wed, 18 Nov 2009 07:50:47 -0600
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Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org
Subject: Re: Boot with ZFS on single disk: "ZFS: i/o error - all block
 copies unavailable" [was: Re: GPT boot with ZFS RAIDZ "ZFS: i/o error - all
 block copies unavailable"]
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On Wed, 2009-11-18 at 01:17 +0100, Emil Smolenski wrote:
> On Tue, 17 Nov 2009 23:33:41 +0100, Robert Noland <rnoland@freebsd.org>  
> wrote:
> 
> >> Should I file a PR? I would
> >> like to help in debugging it (however my skills in low-level C aren't
> >> strong enough to do it on my own).
> 
> > Ok, the first thing I would like to see is "zdb -uuu".
> 
> # zdb -uuu pgpool
> Segmentation fault: 11 (core dumped)

Ok, this is disturbing...  It works fine for me on -CURRENT / amd64 and
reports the root block pointer, which is what we need to locate the MOS.

robert.

> # zdb
> pgpool
>      version=13
>      name='pgpool'
>      state=0
>      txg=439808
>      pool_guid=3920915583055727184
>      hostid=1642959122
>      hostname='unset'
>      vdev_tree
>          type='root'
>          id=0
>          guid=3920915583055727184
>          children[0]
>                  type='disk'
>                  id=0
>                  guid=5859773264564918193
>                  path='/dev/da0'
>                  whole_disk=0
>                  metaslab_array=23
>                  metaslab_shift=35
>                  ashift=9
>                  asize=4500799356928
>                  is_log=0
>                  DTL=260
> 
> > I don't see an
> > obvious issue with single disk reads.  My own setup uses 2 x 1TB
> > currently.  Failing to read the MOS is basically the first read attempt
> > from the pool, in fact it is the read that attempts to mount the pool.
> 
-- 
Robert Noland <rnoland@FreeBSD.org>
FreeBSD