So seems you can pick and choose which option you want whether it be raid or this X-raid they speak off.
Supporting hardware accelerated RAID (Redundant Array of Independent Disks) levels 0, 1, 5 and ReadyNAS’s own X-RAID™ technology, ReadyNAS ensures full data redundancy with protection against hardware failure – something previously only available in high end servers. If one drive fails, the data volumes can still be rebuilt with the remaining drives. Without RAID, once a failure occurs, you risk losing all of the data stored on the drive.
ReadyNAS’s Patent Pending X-RAID technology automates the volume expansion for you as you scale from 1 HDD to 4 HDD. Most NAS devices on the market aren’t future-proof. You can’t add or replace disks for larger capacity. ReadyNAS allows you to start with one disk, then add the additional drives over time, without reconfiguring the system and shuffling the data. Additionally, as disk capacity becomes larger and cheaper, you can replace all four disks, one-by-one, while X-RAID automatically manages the RAID details for you.