Home > Data Protection > PowerProtect DD Series Appliances > Dell PowerProtect Data Domain DD9410 and DD9910 > Continuous fault detection and healing
Regardless of the software safeguards in place, it is the nature of computing hardware to have occasional faults. Most visibly in a storage system, disk drives can fail, but other more localized or transient faults also occur. An individual disk block might be unreadable, or a bit flip error could occur on the storage interconnect or internal system bus. For this reason, DD OS builds in extra levels of data protection to immediately detect faults and recover from them to ensure successful data restore operations.
RAID 6 is the foundation for PowerProtect Appliance continuous fault detection and healing. It protects against two disk failure, disk read errors during reconstruction, guarantees RAID strip consistency, and verifies data integrity after writes. Each storage shelf includes a global spare drive, which automatically replaces a failed drive anywhere in the Data Domain system. When the hot swappable failed drive is replaced by Dell, it becomes a new global spare.