Ars Technica points out that although Apple has supported IP failover -- which allows one machine to pick up services in the event another fails -- in its server lineup since Mac OS X 10.3, PowerPC-based and Intel-based Macs can't be mixed in this equation. In other words, a PowerPC-based Mac cannot serve as a failover for an Intel-based Mac, and vide versa.
An Apple Knowledge Base article on the subject states:
- IP failover does not work with Intel-based Macs With Mac OS X Server 10.4.7 (Universal) or later through 10.4.8, IP failover does not work with Intel-based Macs. This document will be updated as more information becomes available.
- Do not use mixed architectures in failover pairs Do not mix Intel and PowerPC architectures in failover pairs. For example, if the master server is a Xserve Quad Xeon, do not use a Xserve G5 as failover. Conversely, a Mac Pro (Intel-based) should not be used as failover for a Xserve G5 (PowerPC-based).