Home > Data Protection > PowerProtect DD Series Appliances > PowerProtect Appliance Data Invulnerability Architecture > End-to-end verification
Because every component of a storage system can introduce errors, an end-to-end test is the simplest path to ensure data integrity. End-to-end verification means reading data after it is written and comparing it to what was sent to disk, proving that it is reachable through the file system to disk and that the data has not been corrupted. When DD OS receives a write request from backup or archive software, it computes a checksum for the data. The system then stores unique data to disk and reads it back to validate the data, immediately correcting I/O errors. Because data is validated after writing to disk and before being released from memory (NVRAM), correcting I/O errors does not require restarting the backup job.
End-to-end verification confirms that the data is correct and recoverable from every level of the system. If there are problems anywhere along the way—for example, if a bit has flipped on a disk drive—it will be caught. Errors can also be corrected through self-healing, as described in Fault avoidance and containment. Conventional, primary storage systems cannot afford such rigorous verifications; however, purpose-built backup appliances require them. The tremendous data reduction achieved by Data Domain global compression reduces the amount of data that needs to be verified and makes such verification possible.