I wanted to boot my home truenas box off usb flash, but I also know how flakey usb flash can be, so I use a pair of drives in a zfs mirror.
I would not recommend this setup, Any real drive would be better. I just hated wasting drive bays for the non-critical boot/system partition. In my defense despite burning through many cheap usb drives I have not lost the boot yet, however I do keep a new spare drive taped to the unit.
I had grand plans to make a giant USB ZFS volume from tradeshow thumb drives in bulk.
It lasted a couple evenings while I bumped into apparently every Linux USB driver/chipset issue possible trying to drive a couple hundred drives via cheapo AliExpress USB hubs.
It was fun times, but even more useless than I originally thought it would be. It was amusing to get >1GBps for a minute or two across 256 crappy thumb drives though!
From 2009, what I think was a famous video on which some kids in the UK put together a 6-gigabyte RAID with 24 256-gigabyte Samsung drives: https://youtu.be/26enkCzkJHQ
I would not recommend this setup, Any real drive would be better. I just hated wasting drive bays for the non-critical boot/system partition. In my defense despite burning through many cheap usb drives I have not lost the boot yet, however I do keep a new spare drive taped to the unit.