Using pairs of HotStandby (HSB) servers might not be optimal for every use scenario. If near-instantaneous failover is not required, you might not be able to justify the expense of having a secondary server for every primary server. At the other extreme, some business cases might need extra reliability and also warrant the resources to purchase additional spare machines so that a spare machine can be used as the new secondary server if the original primary server cannot be repaired quickly.

To help you to reduce costs or increase reliability, HSB supports various alternatives to the ‘N+N’ or ‘2N’ standard hot standby model (in the standard model the number (N) of primary and secondary servers is the same). The following topics discuss the alternative options: