Converting mirror to RAIDZ1

TrueNAS General
1

Hey everyone, I’m very new trueNAS and servers in general so I do apologies if I get things wrong.

So a few months ago I built my first TrueNAS community version server with one nvme for the OS and two 12tb hard drives for storage. When setting it up the only option available was ‘MIRROR’ so I selected that one. I was happy with my 12tb usable storage.
I now want to add two more 12tb hard drives to this creating 36tb total usable storage… However, after putting them in, the only option is to add the two as a mirror creating a total of 24tb of usable data. As I’ve found in my research, converting a MIRROR to RAIDZ1 is not possible and I have no idea how to backup the almost 11tb of data i have used on the drives I’m using so I can then destroy the existing pool, recreating the pool as raidz1 and then restoring the data from backup.

I dont know, but is it possible to:

  1. Take out one of my original 12tb drives (this will have my data on it)
  2. Plug in the two new 12tb drives. Go into my server, wipe the three of them and create a 24tb pool with RAIDZ1
  3. Then maybe I can put my other 12tb drive (with all my data on it) in my computer and copy over ALL the data to the server? This would take ages though.
  4. Then finally plug the original 12tb drive into my server that now (hopefully) has all my data on it, and add it to the RAIDZ1 pool. DONE?
  5. This now results in the 36tb total usable storage i wanted?

Is there a better way of doing this? The above plan sound okay to me I guess. But also how do I know which drive to take out of the physical server? or because they are mirrored it doesn’t matter?

Like I said, Im not very knowledgeable about all this and would appreciate some help.

Thanks all!

2

Good reading, good understanding and good plan. (I trust you’ve learned about the space reporting issue from raidz expansion. To avoid that, you’d need more drives for backup, or to use CLI to create a degraded raidz1.)
Always track your drives by serial number so you know which drive to keep and which drive to recycle in the new pool the one that was offlined). If you split the pool (CLI), it wouldn’t matter, as each drive would be a self-standing independent pool.

This, however, appears to imply that you have no backup of the data. And this is bad. ZFS is not a backup.