FreeNAS supports various volume layouts depends on how many hard drives on your systems. FreeNAS supports the following layouts which can be defined or configured through Volume Manager.
- log device
- cache device
To read more about the differences and system requirements for each layouts above, please visit this official manual page.
On this tutorial, I am going to show you how to create a mirror ZFS volume on FreeNAS. To create a mirror volume, you will need two hard drive with the same size. First, add or attach the physical hard drives to FreeNAS server. Or, if you install FreeNAS on a virtual machine, make sure you add 2 more hard disks to the system.
Then, go to Storage | Volume Manager
If you have 4 hard disks, you still be able to use mirror layout by dragging the layout button as follow
Next click Add Volume to start the process. This process will take some times depends on the size and number of disks. When finished, you should see your new volume is ready.