Questions regarding parity drives

[BambiBoy]

I'm planning on making a multi purposed server with unraid, and just want to clarify questions about storage before buying drives (as that is the most expensive).

 

The plan is to initially start with 3x12TB drives with one setup in parity. I currently understand that you can add additional drives as you want as long as the capacity is lower than the parity drive. Hence the choice of going big to start, and be able to add 12TB if the prices get lower in the future or add 8TB drives in the rare case that the server gets filled up.

 

If/when I add more drives, I want more parity drives to add more redundancy.

Can you add another parity drive to the existing server?

 

Say i buy 2x8TB drives to add to the existing server,

Can the drive I want to add as a parity drive be a 8TB drive, or is the relation transitive and won't work as there are 12TB drives in the pool?

 

The reason for the 2nd question is that there is a site selling cheap 8TB NAS drives, but are limited to 2 per customer. So instead of adding 4TB, I could theoretically add 8TB.

 

In advance, thank you for all answers (never built a server before).  

[trurl]

You can have a maximum of 2 parity drives. 

 

Each parity disk must be at least as large as any single data disk.