how to simulate a drive failure and replace in same slot

[genfoch01]

Version:
TrueNAS-12.0-U1

I have a pool with 4 sata drives. i wanted to simulate a drive failure and go through the replacement process (i am 100% new to freenas )
so read the following : https://www.truenas.com/docs/hub/tasks/advanced/disk-replace/

I removed the drive and the pool showed degraded and the drive showed "removed" then i attempted to offline the drive but got an error

[disks] Item#0 is not valid per list types: [disk] null not allowed (i attached the full error message )

then realized the instructions above appear to use an empty slot to put a new drive in which i don't have.

so i put the drive back in and it appears to have resilvered the drive (RESILVER Status: FINISHED Errors: 0 )

but this leaves me with 3 questions
a) what is the proper way to simulate a failed drive for testing replacement procedures
b) how do i replace a drive with no free slots except the slot with the bad drive
c) what is the error message i got and did i get it because i did something wrong?

thanks for your time!

 

[tiberiusQ]

TrueNAS 12: Replacing Failed Drives

Connecting With Us--------------------------------------------------- + Hire Us For A Project: https://lawrencesystems.com/hire-us/+ Tom Twitter https://...

www.youtube.com

 

[genfoch01]

Thanks for the link !