Passive Backup
A passive backup member can take over in the event that the main member fails. It is useful in an environment where the main member is powerful enough to process searches on a daily basis, but where a less powerful backup member can be used for handling search requests for shorter periods of time during for example server maintenance or restarting.
Parallel Backup
A parallel backup member is used when you want to maximize search performance. The backup member “competes” with the primary member in processing and delivering search results to the union server. This way, the client that searches the archive will always receive the fastest possible search result. If the primary member fails, the backup member will process all search requests until the primary member is back in operation.
Round-Robin Backup
A round-robin backup member will processes half of all searches from the clients in the system to reduce load on the primary member. In a system with a large number of users and much search processing, this type of solution can greatly improve search response times. The search requests are evenly distributed between the primary and the backup member, sending the first request to the primary member, the second to the backup member, the third to the primary member, and so on.