Commvault Index Cache

The index cache is the directory where index data is located. Index data is a record of all files, folders and objects that are backed up as part of a data protection job (another name for backup). The index cache is very important to maintain as it enables browsing of backed up data. Without the index cache it would impossible to know what files or folders were backed up, and individual file or folder restores are not possible. As part of any backup job, the index data is written in two places: Index cache, and the backup destination. If the index cache is accidently deleted, or the index data goes beyond its retention period, the index data can be restored by reading it from the backup destination. When you click on a backup job and select browse, it will read the index data from the index cache. If it cannot, it will ask for the index cache to be restored from the backup itself. Commvault maintains a record of where the index data is located on the backup media and uses that media to restore it.

The index cache can either be located on a local drive or a network share. If it is located on a network share, it can function as a shared index cache where several media agents can share one index cache. The advantage of this is that instead of putting the index cache on several servers and taking up space, a shared index cache places the index cache in one central location. The rule of thumb when calculating the space required for an index cache is 4% of the entire data the media agent will be used to protect. So if the media agent is used to protect 10 TB of data over a period of 6 months, you would need 409 GB of space.