Cyclic Redundancy Check (CRC) Validation
The integrity of backup operations can be ensured by enabling Data Integrity Validation options from the MediaAgent properties.
Commvault provides CRC validation for the following:
- When data from clients travel over a network to a MediaAgent, and
- Whenever data is written by a MediaAgent to a secondary storage media
Note: The data integrity validation can use up to 64 KB as the block size and depends on the data buffer size sent from the client to the MediaAgent.
How It Works?
For Write Operations:
When a backup is run, the CRC validation works over the network if the CRC is enabled on the network and is written on the media if it is enabled on the media, in the following manner:
- The client generates a CRC from the data that is being backed up.
- The data is sent over the network to the MediaAgent.
- Another CRC is generated on the MediaAgent based on the data received.
- If network CRC validation is turned on, then the CRC generated from the client and the CRC generated on the MediAgent are compared. For more information, see Enabling Data Integrity Validation on Network.
- In case, there is a mismatch, it is indicative of network corruption and the data is sent again on the network.
- After successful validation, the CRC is written on the media as part of the backup if CRC is enabled on the media.For more information, see Enabling Data Integrity Validation on Media.
For Read Operations:
During read operations like restores, data verification and auxiliary copy etc. the CRC validation works in the following manner:
- Source MediaAgent reads the data available on the media.
- The read operation generates a CRC which is compared against the CRC that was saved during the backup (If CRC was enabled while running backups).
- In case, there is a mismatch, it is indicative of corruption.