I made a pool with a single drive for testing purposes in Truenas Scale and it works well. I would now like to add redundancy to the pool and put it into production without losing the existing data. Is there a way to mirror this drive? Do I just add a Vdev to the pool? Or do I need to clear the drive and create a new pool with 2 hard drives?
ZFS allows turning a single disk vdev into a mirror vdev. How that looks specifically in the TrueNAS Scale UI I don’t know. But just make sure you aren’t adding an additional vdev, that would be stripe instead of mirror.
Found it. It’s “EXTEND” in the ZFS pool section.
Yeah you don’t want that. If either one of your drives fail then the whole pool is lost. You are stripping your single drive.