Using GTP and glabel for ZFS arrays

[Dan Langille]

Thank you to all the helpful discussion.  It's been very helpful and 
educational.  Based on the advice and suggestions, I'm going to adjust 
my original plan as follows.

NOTE: glabel will not be used.


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 1024 -s SOMEVALUE -t freebsd-zfs -l disk00 ad0

The -b 1024 ensures alignment on a 4KB boundary.

SOMEVALUE will be set so approximately 200MB is left empty at the end of 
the HDD.  That's part more than necessary to accommodate the different 
actualy size of 2TB HDD.

Repeat the above with ad1 to get disk01. Repeat for all other HDD...

Then create your zpool:

zpool create bigtank gpt/disk00 gpt/disk02 ... etc


This plan will be applied to an existing 5 HDD ZFS pool.  I have two new 
empty HDD which will be added to this new array (giving me 7 x 2TB HDD). 
  The array is raidz1 and I'm wondering if I want to go to raidz2.  That 
would be about 10TB and I'm only using up 3.1TB at present.  That 
represents about 4 months of backups.

I do not think I can adjust the existing zpool on the fly.  I think I 
need to copy everything elsewhere (i.e the 2 empty drives).  Then start 
the new zpool from scratch.

The risk: when the data is on the 2 spare HDD, there is no redundancy. 
I wonder if my friend Jerry has a spare 2TB HDD I could borrow for the 
evening.

-- 
Dan Langille - http://langille.org/