Help Planning Storage for new build

[NasKar]

I'm building a new system and trying to plan it's implementation while waiting for the motherboard to arrive.

Currently I have 6 x 8TB WD Red drives in RAIDZ2 and have 6 x 4TB WD Red drives not being used currently. I would like to keep my current system working while building and testing the new build (mem test and CPU stress) and possibly use the 4TB drives as a backup. Then swap the drives from the old to the new server.

As my new case will hold 16 HDD should I add 2 additional 8TB drives to make an 8 drive RaidZ2 vdev with the option to add a second 8 drive RaidZ2 in the future or just stick with the 6 drive RaidZ2? I know I will have to destroy the pool to do that but if I have a backup (using replication) it won't be an issue.

Slideshow explaining VDev, zpool, ZIL and L2ARC
Recommends 2 vdev be the same number of drives and both RaidZ2.

Should I Install the 6 x 4TB drives in new build as RAIDZ1 to increase my storage space and replicate my old system to the new one as a backup before switching the drives from one server to the other? Then after all the data is transferred change to a 6 x 4TB RaidZ2 for future backup. My current pool is 11.6 TiB so I don't think it will fit on 6 x 4TB RaidZ2. (11.4 TiB with 80% usage)

Another option would be to leave the 6 x 4TB drives in RaidZ2 and just backup my media directory to transfer back to the 8 x 8TB RaidZ2 that I would create. I already have a backup of my jails data directories on my windows machine.

Will the number of drives in a vdev definitely be able to be increased without destroying it and starting over in a future FreeNAS version? If so staying with 6 drives for now would make sense.
I hope this isn't to hard to follow.

 

[CraigD]

As my new case will hold 16 HDD should I add 2 additional 8TB drives to make an 8 drive RaidZ2 vdev with the option to add a second 8 drive RaidZ2 in the future or just stick with the 6 drive RaidZ2? I know I will have to destroy the pool to do that but if I have a backup (using replication) it won't be an issue.

If you have a 16 bay case use it I would buy 2 x 4TB and 2 8TB drives

Create 8 wide 4TB RAIDz2 vdev in the new system can copy everything to it, make sure it is working correctly (Both systems have a complete copy of all data)

Add an 8 wide 8TB RAIDz2 to the pool at a later time

Have Fun

 

[NasKar]

If you have a 16 bay case use it I would buy 2 x 4TB and 2 8TB drives

Create 8 wide 4TB RAIDz2 vdev in the new system can copy everything to it, make sure it is working correctly (Both systems have a complete copy of all data)

Add an 8 wide 8TB RAIDz2 to the pool at a later time

Have Fun

I decided to buy 2 more 4TB drives to put into the new build to make 8 all together. That would give me 20TB of usable space. I could then play around with replication etc and use my existing NAS as a backup machine. Added bonus of not having to take it apart to swap the drives. Most importantly it makes so I'm not in a hurry and can wipe out the new build and start from scratch if I need to. Thanks for giving me the idea.