We require a 12 month contract for the 1U RAID5 Storage Vault unit. The external USB rental drives do not have a contract.Within 1 business day of being notified of a malfunctioning drive, a new drive will be installed and your RAID will automatically rebuild. Your RAID can suffer a single drive loss without losing any data.No, because this is direct-attached storage it will only connect to one mini. You can share the volume between machines by using file sharing though.The advertised volume sizes are after the RAID array is created. Your usable space is just slightly less than the advertised volume size.Currently we use a USB3 connection but as new technologies become available (such as Thunderbolt) we will strive to offer the fastest connection available for your mini.