It means that a disk goes bad and you lose the data. Typically there is some form of protection. I use standard raid 10 which is a bit dated but modern approaches like erasure coding are getting more common. Even if it’s JBOD, you should have a copy of the data in case a drive dies. That’s the value of like raid 5 since it gives you most of the drive space and tolerates a drive failure. RAID is available in software but I’m still using older LSI hardware controllers. A RAID1 mirror would basically be similar to just copying files from one drive to another manually. You get half the storage space but don’t panic when a drive dies. The thing is that drives do die. They are viewed as consumables and thus the question is always WHEN not IF they will die.

Dudes just out there raw dogging those drives. That takes some guts man. Not sure I have it in me to take an approach like that but it’s something I aspire to. For now, it’s rclone replication.