When an index volume becomes full, Enterprise Vault automatically creates a new one. In the Administration Console, the Advanced tab of an archive's properties shows the number of index volumes.

Each new index volume does not have the same index root path as the previous one. The new location for the new index is a random selection from the Indexing Service's open index root paths.

If an archive has more than one index volume, the initial search is performed against the current index volume, which contains the most recently-archived items. To view search results from earlier index volumes, you must choose a date range from a list. The date ranges correspond to the archived date range of items in the index volumes.

Rollover is more likely to occur for File System Archiving archives, Journal archives, and Public Folder archives than for normal mailbox archives.

Rollover archives created before Enterprise Vault 6.0 SP1 are not merged back into the master archive. Archiving continues to the current rollover archive, and that archive's index expands to multiple index volumes as necessary.