I second this, I don't hate that hexos trips out and alerts me to an unsecure drive state when I add single drive vdevs but since I had to do so in the truenas UI I clearly know enough to be able to do so, so perhaps these warnings are unnecessary as Im likely fully aware of the risks...
For my specific application, I really am not interested in redundancy at all, at least not with this operating system, I have several servers deployed in my homelab with close to a petabyte of teared storage solutions were I have plenty of redundant targets and also an offsite hyper compressed archive of the vitals and also cloud targets for configs and documents were it makes a ton of sense to use expensive cloud storage... My needs for hexos is to have an easily deployed on commodity hardware hybrid open target for samba filesharing and app hosting for everyone else that I don't necessarily want to provision privileges to very very expensive resources already in place and I will also use it myself for personal use were I may want to share that space with these other people, like media and games and other files and I can escelate the backup of that shared target to a secure archive in my more enterprise setup...
No I want to be able to deploy a low cost mini itx system that only has 4 3.5in HDDs and a single 2.5in sata SSD and 2 m.2 nvme targets were ill have approximately 64TB of space with the 3.5s and a 4tb sata SSD and 2 2tb nvme targets all on a low cost AliExpress special itx motherboard that has 10gb copper via AQC113 Ethernet nic and dual 2.5gb nics via Intel i226 and a basic but sufficient for the application Intel n100 chip were I have enough bandwidth to 2 nvme SSDs to act as a high speed target for que and a semi fast sata SSD for split partitioning for slog and meta and extra cache to supplement the 32gb(the board only has a single DDR5 slot and is limited to 32gb at 4800mhz) of RAM that is primarily leverage as a write cache and also some scratch space for small file muiti user access like document sharing and also space for application folders and any requisite files needed for any VM we may want to tinker with collectively and also the hexos install with be on a small 256gb sata SSD because it is only used for the base install...
I'm ok with a little capacity loss by using a raidz2( I think it's called raidz2 for a 3+1 vdev) for some peace of mind that if I lose one of the 16tb drives due to failure I can replace it and rebuild the target in case catastrophe happens between the failure before the scheduled rsync opp but that only for the 3.5in HDDs I don't need any redundancy for any of the solid state targets and I'd like to not be screamed at by the command deck when it detects that there are single device vdevs in the configs and just makes them unaccessible all together so here's hoping this is remediated fairly quickly as again I understand the risks, I don't need any handholding and if I lose data due to my own carelessness that is on my and a risk I was willing to take otherwise I wouldn't have configured it that way deliberately in the harder to use truenas UI... Just sayin