BlueCat Crossover High Availability (xHA) provides disaster recovery through the use of redundant servers: xHA makes two DNS/DHCP Servers function as a single server. If one of the servers fails for any reason, the other takes its place and continues providing services.
The pair appears as a single server for DNS queries because both servers share an IP address. Each server in the pair has its own IP addresses for management through Address Manager.
Supported xHA pairs
| Hardware appliance 2 | Virtual machine 2 | |
|---|---|---|
| Hardware appliance 1 | xHA supported | xHA not supported |
| Virtual machine 1 | xHA not supported | xHA not supported* |
Supported xHA configurations
| Physical pair | Virtual pair | |
|---|---|---|
| xHA Backbone connection between pair (eth1) | Mandatory | Mandatory |
| Different software versions on each node | Not supported | Not supported |
| Different architecture on each node | Not supported | Not supported |
| w/ non-BlueCat failover enabled** | Not supported | Not supported |
Note: *Only supported where
latency between the two virtual machines is roughly equivalent to two physical
appliances and where the two virtual machines aren't on the same physical hypervisor
host. If the latency between the virtual xHA pairs exceeds that of two physical
appliances, BlueCat recommends foregoing xHA in favor of the failover capability
provided by the hypervisor (if one exists), though we may not officially test/support
such features. **Such as VMware vMotion or Fault Tolerance.