Setup for 314 with WD Red 6 tb

1. Yes, well about 16.5TiB.
2. Yes, there are no volume size limitations on those units.

Well the 516 has a faster processor and the ability to expand is a big advantage. You'll also find it easier to use use Raid 6 which is a good idea when you are using such large drives.
Have you considered the 316 - same processor as the 314 but with 6 bays.

The 6 bay units have internal power supplies while the smaller units use external.

First, thanks so much for the very quick reply.

Yes, I have considered the 316, that is what I really meant in my original post, thanks.

So if I go Raid 6, if I start with 4x5tb, then I can have about 12tb?

and add two more later for about 20tb single vol?

You are very right, I should think about RAID6 with these large drives, thanks!

You presumably mean 4 x 6 tb as you originally mentioned. With raid 6, you'll get an 11TiB volume which will then increase by about 5.5tb with each disk addition.
See this:
http://ram.kossboss.com/xraid/

How are you going to backup the new nas?

There are 5 TB drives (WD50EFRX for instance).

Raid-6 with 4x5TB -> 10 TB or 9 .1TiB 6x5TB -> 20 TB or 18.2 TiB
Raid-6 with 4x6TB -> 12 TB or 10.9 TiB 6x5TB -> 24 TB or 21.8 TiB

Great, thanks to all for help!!!!

So I ordered the 316 and 4x6tb WD reds.
I'll begin with that for the 10.9 TiB with RAID6.

Then add two more at later date for the full 21.8 TiB. That will work, right?

Also when I get my 316 and the 4x6tb, anything special I need to do first?

I hoping I can just load the 4 drives directly into the unit, power it on and let it build.

(or do I need to load the drives, interrupt it during build, do a firmware update and reset?)

Put in 1 drive, boot and update the firmware.
Power down, insert all the other drives then factory default the unit.
Login to the GUI and disable Xraid ( you do not need to wit for the resync to finish) then destroy the volume. Create a new volume in flexraid , setting it up using all 4 disks and setting raid 6. After it starts to build, change to Xraid again - again you do not need to wait for the resync to finish).
It will probably ask if you want to destroy the volume, say yes. It should then change to Xraid , but with dual redundancy (raid 6) and start the build again.
This method is quickest, but will lead to the default shares being deleted. This may not be a problem for you though.

Thanks again!!

I logged into GUI after inserting 4 new drives, but don't know how to interrupt the sync, disable XRAID and destroy volume.

***note: and maybe this is where I went wrong. I got the 316 before the drives, so I popped a 256 gig drive in yesterday and updated the OS to 6.2. Then today when I got the 4x6tb drives put them in and did factory default. Now I can't see where to interupt the sync, disable XRAID, etc. Is this because I didn't put a single drive of new set in as you said and there is NO volume to disable XRAID and wipe the Volume?

You go to the Volumes tab and you should see a X-RAID button at the far right. Click on this and confirm you wish to disable X-RAID.

Select the volume, click on the settings wheel and select DESTROY.

so.... would it be best to power off, pull three of the new drives, and let a single sync up first, then power down, put the other three drives in, factory default, an would I now at least be able to interrupt the sync, disable XRAID, wipe volume?

You should be able to interrupt the sync now.