Setting up an expandable RaidZ2

[Thousandbuckle]

Hello all, I am getting ready to start allocating storage for my FreeNAS server and need some feedback from ya'll on how to achieve my goals.

I am starting off with 4 x 2TB WD Red Drives. My goal is to have a RaidZ2 so that I have a two disk fault tolerant storage. I would like to be able to expand the volume size in a year from now without having to destroy the whole storage volume and need some help on how to setup the initial volume with vdevs.

I have read the document by cyberjock which outlines very nicely the concepts of ZFS but how to create this in the GUI and if I understand correctly the concept is what I need assistance with.

If I setup my initial ZPool or Volume as below it would be a RaidZ2 Volume with 4 x 2TB drives in a VDEV giving me 4 TB usable space. If in a year from now when I want to add more space am I limited to the number of drives I can put in the new VDEV to add to the Pool? Example could I add 2 x 2TB drives or would it have to be 4 x 2TB drives? Once I added the appropriate number of drives I would create a new VDEV and the add that VDEV to the orignal ZPool?

Can some one please confirm if my understanding is right and that what I am doing will allow for future expansion?

 

[indy]

Your understanding is correct.
Once a vdev is added to a pool it can not be edited, however you can add as many vdevs to a pool as you like.

 

[Thousandbuckle]

But just to be clear, I assume I am limited to the number of drives I would use to create the new VDEV to add to the existing pool? I know the documetation says you can add VDEV's that have different configurations to the Pool but is not recommended. In my case I would create a second VDEV with 4 drives (mandatory) since the original Volume is a RaidZ2 to have the same VDEV configurations?

I am also confused if the Pool or the VDEV built as the RaidZ2?

 

[danb35]

The vdev is built as a mirror, RAIDZ1, RAIDZ2, etc. The pool is striped across however many vdevs it contains. There's no requirement that the vdevs in a pool be similar in any way--you could have a pool consist of a single disk vdev and a RAIDZ3 vdev (this is what's known as "hating your data", and is a Very Bad Idea (tm), because failure of that single disk would result in loss of all your data). So, if you have an existing pool consisting of a 4 x 1 TB RAIDZ2, you could expand the pool by adding a 6 x 2 TB RAIDZ2 vdev, resulting in a total net capacity of ~ 10 TB. Or, you could add 2 x 1 TB drives in a mirror, which would bring the net capacity to 3 TB.