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Date: Tue, 4 Jan 2011 18:44:09 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: Chris Brennan <xaero@xaerolimit.net>
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	(wonkity.com [127.0.0.1]); Tue, 04 Jan 2011 18:44:10 -0700 (MST)
Cc: Bruce Cran <bruce@cran.org.uk>, Ian Smith <smithi@nimnet.asn.au>,
	FreeBSD Questions <freebsd-questions@freebsd.org>
Subject: Re: a new hard-drive in a 2y/o laptop
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On Tue, 4 Jan 2011, Chris Brennan wrote:

> On Tue, Jan 4, 2011 at 3:56 AM, Ian Smith <smithi@nimnet.asn.au> wrote:
>
>> On Mon, 3 Jan 2011 16:31:17 -0500, Chris Brennan wrote:
>> [.. trimming ccs, selectively quoting and de-gmailing a bit ..]
>>
>
> Trimmings! Oh nevermind. I don't know what possessed me to  go and look
> at the debug window. But I do and I see the following.
>
> GEOM: ad4: the primary GPT table is corrupt or invalid.
> GEOM: ad4: using the secondary instead -- recovery strongly advised.
>
> This is even after zero the beginning and the end of the drive ....
> Something is hinky!

Today I also found that zeroing the beginning and end of the drive 
didn't seem to be enough.  I had the start of a huffy email about how 
hard it was to calculate the end of a drive in blocks, and how dd didn't 
have a negative oseek to seek backwards from the end.  But then I 
checked gpart(8)... and it turns out that

# gpart destroy -F da0

works.  Be very careful that you've got the right drive there, of 
course.