What disks should I use?

[kenzu]

Hi

I have a pile of disk of different size and age.
My proplem is I cannot figure out if I should use smaller old disks and save my newer disk for later use. (when I need space or older disk die)
My system is a 4 bay Hp Microserver and my data size is atm 3.3TB.
The disks I have is:
4 x 14TB (almost new)
2 x 6TB
6 x 4TB

So the question is:
3 x 14TB raidz1 with 1 spare
4 x 14TB raidz1
4 x 4TB raidz1 with 2 spares on the shelf
2 x 4TB mirror + 2 x 6TB mirror
2 x 6TB mirror + 2 x 14TB mirror

Speed is not important, and 1 disk failure is fine for me.

Thanks

Jesper