Expand Storage TrueNAS COre 13 RaidZ2

Hi there, I need to know the options to expand the storage on Pool. I am currently at 97% utilised and I need to add more storage space.
The true NAS is being used for backup Archives.

I have 9 x 18TB disks being used right now.

I want to add another 2 x 18 TB drives.

I cannot rebuild the Pool and I beleive I need to create another VDEV. There is currently only one VDEV associated to a storage Pool.

Can I one VDEV with 9 Disks and another VDEV with 2 Disks. I beleive this is not recommend in terms of balancing. I need to increase the storage on the TrueNAS server.

Yes, but then you would be stuck with it.

As it stands now, and I could be wrong, if your pool is not solely comprised of mirror vdevs, you cannot remove a top-level data vdev.

So the additional 2 drives you add as a new vdev cannot later be removed to convert them into members of a larger and wider RAIDZx vdev.

Hi there, how do confirm the details mentions regarding mirror?

I am running out of disk space, and I cannot rebuild the Pool.

I only have 4 empty disk slots.


What do you mean?

EDIT: I think I understand.

From the zpool remove OpenZFS documentation:

You are not wrong, and I’m not aware of any plans to change this–RAIDZ expansion has been Coming Soon™ for the last seven years or so and is now expected to land in SCALE by the end of the year, but neither RAIDZ vdev removal nor RAIDZ reduction is anywhere in the cards.

The pool status page in the web GUI will tell you your pool layout.

Then you’ve designed your system very poorly in terms of future expansion.

With all of that said, yes, you can add a two-disk mirror vdev to your existing nine-disk RAIDZn vdev. You’re correct that this configuration isn’t recommended, but it is possible, and the GUI will let you do it. But you won’t be able to remove it in the future without destroying and recreating the pool.


Hi there, I have inherited this TrueNAS. There is one Pool called DATA configured as RAIDZ2. There is only 4 slots left. The purpose of this exercise is to increase space. I am unsure about the creation of the VDEV’s. I built a test TrueNAS and I was not able to add another VDEV unless it had 4 disks.
The below is my test TreuNAS. The version of this test box is different from the production. I cannot see any option to allow me to create another vdev with only 2 disks.

4 is the minimum for raidz2.
You can create a vdev with a single drive (STRONGLY ADVISED AGAINST!!!). You can stripe your (inherited) raidz2 with a 2-way mirror, but the resulting pool will have an obvious point of failure in the lower resiliency of the 2-way mirror. You may expand the 2-way mirror to a safer 3-way mirror.
Raidz expansion could help you, but at 97% you probably cannot afford to wait for this feature.

Mid- to long-term, the only way out of this situation and back to sanity is to back up everything, delete the pool and rebuild something better.

Thank You, I have the issue of finding the storage to back the 84TB of data.