The process of upgrading Exchange Server 5.5 cluster systems is tricky because Microsoft doesn't support cluster upgrades out of the box. However, the Exchange 2000 CD-ROM contains a documented procedure that describes several explicit and manual tasks that you must perform to upgrade your clustered system:
- Save the existing Exchange 5.5 databases (private and public).
- Reinitialize the clustered system (i.e., build a new cluster and install a new Exchange 2000 cluster—as if it were a new system).
- Reapply the old Exchange 5.5 databases to the new Exchange 2000 cluster and perform the database upgrade process.
As an alternative, if you have the hardware (at least temporarily), you can install a new Exchange 2000 cluster into the same site as the existing Exchange 5.5 server and use the restructuring approach to move mailboxes from the Exchange 5.5 cluster to the new Exchange 2000 cluster. However, remember that the first Exchange 2000 server in an Exchange 5.5 site can't be on a clustered system because the Site Replication Service (SRS) must run on the first Exchange 2000 server in a site and Microsoft doesn't support SRS on a cluster.