Expanding a ZFS pool in TrueNAS SCALE

Recently, TrueNAS SCALE 24.10 was released and added a long-awaited feature: the ability to expand a ZFS pool. This allows additional disks to be added to an existing pool, increasing its capacity.

This feature is called expand pool in ZFS, but TrueNAS names it as "extend" so that can be a bit confusing. Still, it is the same thing.

According to the documentation, this is the procedure:

1. To do so, go to Storage. Locate the pool and click Manage Devices on the Topology widget to open the Poolname Devices screen.

2. Select the target VDEV and click Extend to open the Extend Vdev window.

3. Select an available disk from the New Disk dropdown menu. Click Extend.
4. A job progress window opens. TrueNAS SCALE returns to the Poolname Devices screen when complete.

This is a really neat feature to have, and I got myself a refurbished HDD (CMR) and added it to my existing ZFS pool. As my existing pool uses SMR drives, things can be really slow... the plan is to slow replace the SMR drives with CMR ones as and when finances allow.

 

To see the actual status of the expansion, the following command can be used in a shell.

zpool status

Or if you want to see a particular pool, for example, a pool called mainpool, use

zpool status mainpool

Meanwhile, after 11.5 days, the expansion of the pool has finally been completed.