In sysadmin terms, they have aimed for data integrity over availability. If a system goes down and they have to replace a disk or a power supply or motherboard

In sysadmin terms, they have aimed for data integrity over availability. If a system goes down and they have to replace a disk or a power supply or motherboard, the data is still safe, and if by chance there's any $5/month users who need to restore data held on that one unit, well they can wait a few hours :-)