16 Bay Server in RaidZ2

[chriscarpenter12]

First time using FreeNAS and still doing research on bsd and zfs. I have plenty of experience with linux and raid 6 in general though.

I have a Supermicro 16 bay case that I'd like to use for FreeNAS, but my question is which drive configuration should I use? Looking through the stickies and recommended settings for zfs in a RaidZ2 I should use 6 drives in a vdev. Currently I have 8x3 TB WD Red drives. Some new some a few months old from another system. My issue is I could create a pool now with a Raidz2 vdev of 6 drives and later down the road add another 6 drive vdev, but would only utilize 12 bays of my 16. What do I do with the other 4? I was thinking I could create a Raidz2 vdev of 8 drives now and later add another 8 drive vdev to use all my bays when I need to expand. This way limiting my parity drives to 4 vs 6 if I added a third vdev for the remaining 4 empty bays. In FreeNAS in virtualbox I was playing with vdevs and settings and it complains about 8 drives in a raidz2 vdev as "non-optimal". Looking for suggestions.
Thank you

 

[Yatti420]

4x3TB red z2 pools/vdevs.. Probably also non-optimal.. But just a thought..

 

[Starpulkka]

Test yourself do you like what you see how variable block sizes settle in raidz2 10hdd +raidz2 6hdd =16hdd or can you bare compromise raidz2 8 +raidz2 8.
I would put big files in raidz2 10 and smaller files raidz2 6.
Yay, the fun has been doubled..