Home > Data Protection > PowerProtect DD Series Appliances > Dell PowerProtect Data Domain DD9410 and DD9910 > End-to-end verification
End-to-end verification means reading data after it is written and comparing it to what was sent to disk, to prove 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. End-to-end verification confirms that the data is correct and recoverable from every level of the system. 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.