Had a Nas with a single 3tb seagate HDD in it.
It ran well for half a year and it was my main backup and a time machine for my dad.

The time came that my budget was allowing a second drive for redundancy so I powered it off, added the second drive and powered it back on.

😐😓😧😭

The drive did indeed die and yes, it was one of those drives with an extremely high failure rate.

My dad was pretty mad that his backups were gone even though he didn't need them.

So my biggest lesson from this was to always encrypt such drives because dads backup wasn't and my files and such weren't either, so someone could restore our hole life's from the drive.
So I can't Rma that fucker.
Zfs at rest encryption ftw!

By the way, writing this I noticed that I didn't need to power the Nas down to add the second drive....
Ffffffffuuuuuuuuucccckkkkkk.

Another more recent thing was a refurb 4tb we red that I bought used for a bargain.
It reported 2 unwritable sectors but I didn't care for the money.

After about a month, it died.
The interesting part is how it died.
It spinns up, gets detected, you can access the data.
You can copy the data.

But after a few moments of continues load, all operations start timing out and the drive either disconnects completely or the zpool degrades and shuts down.

In the first case, replugging brings the drive back untill it does it again.

On zpool degradation only a reboot brings it back.

Put a fan on it in case it was overheating but that didn't fix it.