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To: freebsd-stable@freebsd.org, "Dmitry Sivachenko" <trtrmitya@gmail.com>
Subject: Re: 10/stable panic: softdep_deallocate_dependencies: dangling deps
References: <021AFCAD-7B0B-47FB-AAFF-8F7085C7E1A6@gmail.com>
Date: Tue, 01 Jul 2014 09:57:10 +0200
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From: "Ronald Klop" <ronald-lists@klop.ws>
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On Mon, 30 Jun 2014 14:22:02 +0200, Dmitry Sivachenko  
<trtrmitya@gmail.com> wrote:

> Hello!
>
> I have several machines with rather fresh FreeBSD-10/stable.
>
> They all have 4 SATA drives, I have small gmirrored root+var and the  
> rest of the drive space is mounted as /disk1, /disk2, etc (UFS2+SU).
> When a single disk fails, system panics with  
> "softdep_deallocate_dependencies: dangling deps" message:
> http://people.freebsd.org/~demon/softdep.png
>
> Since all vital data (root+var) are mirrored, I expect OS to stay alive.

Hi,

So /disk1, /disk2 are not (g)mirrored? In that case the system cannot  
handle write failure. Because writes are not synchronous (for speed) there  
is no possibility to return an error to the application.
The OS does not have a notion of 'vital data'. Disk1 and disk2 could  
contain more vital data than root+var as far as the OS knows.

I didn't program the filesystems of FreeBSD, so I might be wrong on some  
reasoning, but this is the idea.

Ronald.