The title could also be``How to change a bad drive in TrueNAS?`` and in my case ``How to upgrade the pool storage space?`` but had it the end it was ``How to trouble shoot during this process?``. The documentation I used can be found had https://www.ixsystems.com/documentation/freenas/11.2/storage.html#replacing-a-failed-disk How to fix a degraded pool state in TrueNAS ? In my homelab environment I am using, one off the disks is bad in my TrueNAS. I had to detach the faulty drive to be able to boot the server up again. To replace the disk you must have a replacement disk from the same size or bigger. Because I have to upgrade my pool to a bigger capacity I will change all my 2TB drives to 6TB drives but for obvious reasons I will begin with the bad one: ``I like my data``. Before replacing the drive I will scrub the pool and set the faulty drive offline (which was not possible because the drive was not connected). Replace the drive and adding it again to the pool has a replacement. T