Previously when setting up a Deduplication Database (DDB) with long term retention we recommended setting up
Primary Copy with 90 day retention
Secondary Copy with 1 to 5 year retention and to seal every year
This recommendation was based on managing the DDB size and maintaining performance.
In terms of DDB size
- there is no limit to the number of secondary tables
- a secondary table will not be deleted until all references in it age
- white space does not get reused
- a secondary table can grow to a maximum of 4GB
The secondary tables for a DDB created in version 11 can contain 256 archfiles per secondary table
The secondary tables for a DDB created in version 11 before Service Pack 14 can contain 16 archfiles per secondary table
The secondary tables for a DDB created in version 11 after Service Pack 14 contain 1 archfiles per secondary table
To manage secondary table bloat inside the DDB, on DDBs created prior to Service Pack 14 you can compact the secondary tables inside the DDB as per https://documentation.commvault.com/commvault/v11_sp17/article?p=12613.htm
In terms of performance we can see degraded performance when a DDB reaches 800 million primary records. With this in mind, as Anthony mentioned, Development have introduced Hozinontal Scaling in Service Pack 17.
Separate DDB partitions are created for virtual machines, databases and file system agens.
In SP17, we will also create a new DDB when a DDB reaches the defined threshold. With the auto creation of DDBs, a new DDB will be created when a DDB reaches the defined threshold, which will result in new sub-clients being added to the policy will point to the new DDB. Any existing sub clients will continue to backup to the existing DDB.
If the DDB is created in SP17 you are not required to create a separate DDB with long term retention.
There is an additional consideration, if resiliency is enabled on your DDB and 1 partition is corrupt. Any blocks that were written while the partition was offline will be maintained on your disk library until the job meets retention.