Help Understanding Creation of Volume

[theprez]

Hello,

I have 8 hard drives (4TB each) and during the volume creation (Storage and Volume Manager) is there any difference where FreeNAS automatically places the drives with 4 on top and 4 on bottom vs. dragging the slider and putting all the drives on one row?

Thanks

 

[danb35]

Yes, the difference is that they're two different pool layouts. See http://doc.freenas.org/11/storage.html#volume-manager

 

[theprez]

Yes, the difference is that they're two different pool layouts. See http://doc.freenas.org/11/storage.html#volume-manager

Thanks, I read that earlier but it's still not clear to me. When a disk is stacked, is that a mirror? I planned to drag my 8 drives into a continuous row vs have 4 on top and 4 on the bottom.

 

[danb35]

Each row is a vdev. So one row is one vdev, two rows is two vdevs. One row in RAIDZ2 is probably a sensible configuration for eight disks.

 

[theprez]

Each row is a vdev. So one row is one vdev, two rows is two vdevs. One row in RAIDZ2 is probably a sensible configuration for eight disks.

Thought I'd throw this in there to help clarify my question:

Other than the storage space difference between the two configuration I'm not entirely sure what else has changed. Said differently, why does one layout have less available space than the other and what are the cons/pros?

Thanks

 

[danb35]

why does one layout have less available space than the other

Because the first layout is creating one RAIDZ2 vdev (with two disks' worth of redundancy), and the second is creating two RAIDZ2 vdevs (each with two disks' worth of redundancy).