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Cyclic Redundancy Check (CRC) Validation

The Cyclic Redundancy Check (CRC) validation verifies the integrity of the data secured by the backup operations and transferred over a network, and the data stored on the media. This data integrity validation is enabled by default.

CRC validation is done on the following:

  • When the data from clients travel over a network to a Backup Gateway

  • When the data is written by a Backup Gateway 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 Backup Gateway.

How It Works?

For Write Operations

When a backup is run, the CRC validation works over the network and on the media in the following manner:

  • The client generates a CRC from the data that is backed up.

  • The data is sent over the network to the Backup Gateway.

  • Another CRC is generated on the Backup Gateway based on the data received.

  • The CRC generated from the client and the CRC generated on the Backup Gateway are compared.

  • In case, there is a mismatch, it is indicative of network corruption and the data is sent again on the network.

  • The data is passed over to the media writer module on the Backup Gateway.

  • New CRC is generated in the media writer module on the Backup Gateway.

    Note

    CRC validation is performed on the Backup Gateway for the following reasons:

    • Network CRC and media CRC are independent configurable options and have their own calculations.
      • Network CRC verifies the integrity of data as it is received over the network.
      • Media CRC is computed on the data received over the network and written to the storage, ensuring the integrity of the data on the mount path.
    • During deduplication, the Backup Gateway generates internal buffers that differ from the data received over the network. These buffers require their own CRC calculations to validate their integrity.

  • After successful validation, the generated CRC is written on the media as part of the backup.

For Read Operations

During read operations like restores, data verification and auxiliary copy, the CRC validation works in the following manner:

  • Source Backup Gateway 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.

  • In case, there is a mismatch, it is indicative of corruption.

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