Expanding zfs+geli pool

[Emre Gundogan]

Hi all,
I have a 4-disk (2TB each) striped mirrored zfs pool consisting of geli
vdevs in the following configuration:

pool:
  mirror1:
     disk1 (2TB)
     disk2 (2TB)
  mirror2
     disk3 (2TB)
     disk4 (2TB)

I'd like to replace those disks with 4TB ones to essentially double the
capacity of the pool. What's the recommended order of disks to 'zpool
offline/replace/resilver (automatic)' in this case? In sequence, or can
I replace them in the following order: disk1 -> disk3 -> disk2 -> disk4
?  Considering that two of the 4TB disks I am thinking of using in the
grown pool are few months older than the others, I thought putting the
older ones in separate mirrors would reduce the risk of pool becoming
unavailable when they fail (possibly both together at the same time).
Does this make sense, and is it possible to replace them in the odd
order I described? Just a note: I only have 4 SATA ports available on
this machine, and therefore can't have both old and replacement disk
plugged in at the same time.

Thank you,
Emre.