[rescue] expanding a ZFS pool: leave slack space?

[Scott Newell]

I've got a 1 TB ZFS pool (2 drive mirror) that I'm going to expand to 
4 TB. Currently the 1 TB drives have partition tables, with the 
partitions and pool a few hundred MB less than the total drive capacity.

When installing the new drives, should I again partition them so the 
pool ends up a bit smaller than the entire drive? If so, what's the 
rule of thumb? 0.1% of the drive? 512 MB? 8 GB?

My concern is that in the future a replacement drive might not be 
exactly the same number of sectors, and if it's too small, the mirror 
obviously won't accept it.

thanks!

-- 
newell  N5TNL