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Date: Mon, 24 Feb 2014 15:55:34 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: Chris Stankevitz <chrisstankevitz@gmail.com>
Subject: Re: gptids are not symlinks to /dev/da*
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On Mon, 24 Feb 2014, Chris Stankevitz wrote:

> Warren,
>
> Thank you for your reply.
>
> On Mon, Feb 24, 2014 at 11:26 AM, Warren Block <wblock@wonkity.com> wrote:
>> Not device name, but a label.  Although the correct one should work in place
>> of a device name.  I use GPT partition labels, but have never bothered with
>> the GUIDs.
>>
>> ...
>>
>> Generated when the structure is created, I think.
>
> Now I just need to find out what is "GPT patition label", a "GUID",
> and "structure creation"!  I will read glabel(8) and see if that
> clears it up for me.

http://en.wikipedia.org/wiki/GUID_Partition_Table is pretty good.

>> smartctl wants a device, but GPTIDs refer to partitions.
>
> Okay, although I am a bit surprised to hear that a GPTID refers to a
> partition.  I'm using FreeNAS and I thought I instructed the zpool to
> consist entirely of unpatitioned disks.  I gather that FreeNAS is,
> somewhere in the process, creating partitions which triggers
> "structure creation" which creates unique GPTIDs.

Probably.  One problem with canned single-purpose software like FreeNAS 
is that it is not as transparent as using FreeBSD directly.