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Whenever a new DDB is created, a fresh copy of signatures and first occurrence of each subsequent data block is written to storage. However these data blocks may already exist in storage with signature contained in the sealed DDBs residing in the MediaAgent or Data Center. The DDB Priming feature looks for signatures in the previously sealed DDBs and uses them to baseline the new DDB. In source-side deduplication, this saves the need for clients to transfer data blocks that are already available in the storage.

This option is not supported on archive cloud storage.

 

Two questions here: 

 

  1. However these data blocks may already exist in storage with signature contained in the sealed DDBs residing in the MediaAgent or Data Center. Data Center? What is a Data Center in CommVault? 
  2. The DDB Priming feature looks for signatures in the previously sealed DDBs and uses them to baseline the new DDB. How the Commvault accomplish it? Does Commvault copy signatures from the sealed DDB to the new DDB? Or does it just query the sealed database at the time of the clients' backup?

Store priming has a very narrow use case and I personally don't recommend using it in the majority of cases. In a nutshell, when you seal an existing non-corrupt store, you start fresh with a DDB with no signatures. When a new signature comes in, the DDB will lookup that signature in the previous DDB, and if found, it will try to copy the block from the library where it exists rather than receiving the block from the client over the network. This should theoretically be faster and saves on network bandwidth, especially for auxiliary copy operations.

The documentation is trying to say the block will be copied locally rather than over the network from a remote client. Data Center is probably not the right term :)

 

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