Using GTP and glabel for ZFS arrays
swhetzel at gmail.com
Thu Jul 22 05:06:02 UTC 2010
On Wed, Jul 21, 2010 at 10:05 PM, Dan Langille <dan at langille.org> wrote:
> I hope my terminology is correct....
> I have a ZFS array which uses raw devices. I'd rather it use glabel and
> supply the GEOM devices to ZFS instead. In addition, I'll also partition
> the HDD to avoid using the entire HDD: leave a little bit of space at the
> start and end.
> Why use glabel?
> * So ZFS can find and use the correct HDD should the HDD device ever
> get renumbered for whatever reason. e.g. /dev/da0 becomes /dev/da6
> when you move it to another controller.
> Why use partitions?
> * Primarily: two HDD of a given size, say 2TB, do not always provide
> the same amount of available space. If you use a slightly smaller
> partition instead of the entire physical HDD, you're much more
> likely to have a happier experience when it comes time to replace an
> * There seems to be a consensus amongst some that leaving the start and
> and of your HDD empty. Give the rest to ZFS.
> Things I've read that led me to the above reasons:
> * http://lists.freebsd.org/pipermail/freebsd-geom/2009-July/003620.html
> The plan for this plan, I'm going to play with just two HDD, because that's
> what I have available. Let's assume these two HDD are ad0 and ad1. I am
> not planning to boot from these HDD; they are for storage only.
> First, create a new GUID Partition Table partition scheme on the HDD:
> gpart create -s GPT ad0
> Let's see how much space we have. This output will be used to determine
> SOMEVALUE in the next command.
> gpart show
> Create a new partition within that scheme:
> gpart add -b 34 -s SOMEVALUE -t freebsd-zfs ad0
Instead of using glabel to label the partition on a GPT disk, use this
gpart add -b 34 -s SOMEVALUE -t freebsd-zfs -l disk00 ad0
You will then see a /dev/gpt/disk00.
Then to create the zpool use:
zpool create bigtank gpt/disk00 gpt/disk02 ...
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