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Date:      Wed, 23 Sep 2015 13:07:49 -0400
From:      Paul Kraus <paul@kraus-haus.org>
To:        Chris Stankevitz <chris@stankevitz.com>, FreeBSD Questions <freebsd-questions@freebsd.org>
Subject:   Re: Name/label/id metadata: how do I make it go away
Message-ID:  <93BD5F1D-9A64-4430-8519-FCF71E817A29@kraus-haus.org>
In-Reply-To: <5601CB85.8070400@stankevitz.com>
References:  <56004C68.4020904@stankevitz.com> <alpine.BSF.2.20.1509212126470.4544@wonkity.com> <5600F0DF.8000805@stankevitz.com> <e1abb521ab324532b3445d26984f5638@SERVER.ad.usd-group.com> <5601A82A.7040304@stankevitz.com> <5601B2AF.7040306@stankevitz.com> <alpine.BSF.2.20.1509221500580.14674@wonkity.com> <5601CB85.8070400@stankevitz.com>

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On Sep 22, 2015, at 17:43, Chris Stankevitz <chris@stankevitz.com> =
wrote:

> And if I want to dig deeper into root cause I can ask ZFS "why do you =
sometimes select from the consumer collection and sometimes from the =
provider collection when putting a pool together".  Or if I don't want =
to dig deeper I can "deal with it" or I can disable diskid using =
kern.geom.label.disk_ident.enable

Assuming 10.x, on boot the ZFS code scans all attached devices and =
attempts to reassemble any zpools that it finds that were owned by this =
system. I suspect which device ZFS uses is based on which it scans (and =
finds) first.

I actually prefer the /dev/diskid/nnn names as those are tied to the =
physical drives. By using them I guarantee that even if a drive =
physically (or logically if drives or controllers are added) moves the =
system can still find and import the zpool. In the early days of ZFS one =
of the best ways to damage a zpool was to rearrange drives so that the =
ZFS label (and cache) no longer agreed with reality. I was in the habit =
of manually exporting critical zpools before making any hardware changes =
and after the changes were complete I would import the pool (sometime =
with new device names). ZFS _should_ be robust enough to handle device =
movement today, but I am slightly paranoid when it comes to critical =
data.

--
Paul Kraus
paul@kraus-haus.org




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