Well not quite. More like "USB connected drives in RAID could be less reliable than internal and software can deal with it. ZFS makes that easier than LVM+mdraid." The downside of LVM+mdraid in my experience is that it needs more commands typed in to repair an array if something's gone wrong. It probably doesn't break much more than ZFS would under the same hardware conditions and it probably can recover from the same conditions ZFS could. USB drives can present more failure modes than internal but one of the points of RAID is to mitigate hardware failures. So I'm considering USB drives as just shittier drivers whose shittiness the software should be able to hide. So far that has been borne out in practice in my anecdata. I've used both LVMRAID (LVM+built-in mdraid) and ZFS with questionable USB drives and both have handled them without data loss and rare downtime, less than once a year. ZFS requires less attention. With all of that said ZFS does of course provide data integrity checking and correction which is a significant plus over LVM+mdraid. It's already saved me from data corruption due to RAM I had no idea had a problem. RAM that passed Memtest86+'s first pass. Little did I know that it fails on subsequent passes... Yes the first and subsequent passes are different. So I'd use ZFS with USB or internal disks whenever I have the choice to. 😂