Unplugging disk under ZFS yield panic

[Fabian Keil]

Gergely CZUCZY <phoemix at harmless.hu> wrote:

> I'd like to ask, whether it is normal behaviour when we're unplugging a
> disk under a ZFS system then on the first write a kernel panic happened.

Sounds familiar. I currently have two PRs open for
reproducible kernel panics after a vdev gets lost:
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/162010
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/162036

Note that the pool layouts are different, though.

> The hardware is a supermicro X8DTH-i/6/iF/6F board with 2x LSI 2008
> fusion MPT SAS-2 controllers, over the mps(4) driver. The disks are
> accessed over gmultipath, and the multipath'd devices are added to a
> ZFS mirror:
> DB
>  mirror-0
>   multipath/DB01
>   multipath/DB02
>  mirror-1
>   multipath/DB03
>   multipath/DB04
>  logs
>   mirror/host1p5
>  cache
>   multipath/SSD03p1
>  spares
>   multipath/DB05
> 
> System is 9.0-RELEASE
> 
> I've unplugged DB03 and on the first write we got a kernel panic.
> Should this be normal behaviour or we're missing something here?

Without a back trace or at least the panic reason one can only
speculate what's going on, but I think it's rather unlikely
that the panic is the intended behaviour and not a bug.

Maybe you can gather some additional information and file a PR?

> On a device removal we're expecting it to moving to the spare disk, or
> using the available redundant disks.

I agree that this behaviour would be preferable to a panic.

Fabian
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