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Date: Fri, 26 Jul 2013 18:40:59 +0100
From: Frank Leonhardt <frank2@fjl.co.uk>
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To: freebsd-questions@freebsd.org
Subject: Re: disk is AWOL
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On 26/07/2013 17:56, Dieter BSD wrote:
> 8.2 amd64
> ad8 is a 3TB Seagate on nforce4-ultra controller
>
> At boot:
> ad8: 2861588MB <ST3000DM001 9YN166 CC4B> at ata4-master UDMA100 SATA 3Gb/s
> DEBUG g_part_gpt.c gpt_read_hdr() ad8 succeeded with pp->sectorsize=512
>
> An hour later:
> # dd if=/dev/ad8 bs=4k count=1 of=/dev/null
> dd: /dev/ad8: No such file or directory
>
> BUT: there was no "ad8: FAILURE - device detached" or similar message
> on the console, in dmesg, or in /var/log/*.  The disk just disappeared
> without a peep from the kernel. What's going on?
>

Is this repeatable? Does it appear when you reboot and then vanish after 
a period of time?

At boot, what does "atacontrol list" say, and what about before and 
after you've tried to read from the drive?