What happens when a disk in my RAID 4 or 5 volume stops working?

Because of the way that RAID 4 and RAID 5 work—by creating parity data, which can be used to rebuild your data, and storing that parity data separately from the data it encodes—one of your RAID 4 or RAID 5 disks can completely stop working and your data is safe.

Read more about how parity data is calculated and stored in RAID 4 and RAID 5 volumes here.