Content Summary : The objective is to document a working configuration of ESRI’s Spatial Database Engine (ArcSDE) 9.x (9.0 and 9.1) and Microsoft’s SQL Server 2000 Enterprise Edition, in an Active/Passive Microsoft Cluster Server (MSCS) configuration. This is in support of an ArcSDE high-availability configuration, which is required for some GIS environments. This report is not all-inclusive and is intended for technical engineers experienced with ArcSDE, SQL Server 2000, and MSCS clusters. Test Hardware and Software Configuration The MSCS test cluster was located in ESRI’s Enterprise Systems Lab (ESL) and consisted of two INLINE Intel-based servers, each running Windows Server 2003 Enterprise Edition. Each cluster node was configured with dual Gigabit network interface cards (NIC). One NIC was dedicated to client network communications while the other was dedicated to real-time cluster monitoring (i.e., heartbeat). The SQL Group virtual IP address and virtual server name, which are used by client application connections, are “moved” via the MSCS software from one cluster node to the other during a failover event. Four public IP addresses are required for an Active/Passive MSCS/SQL Server cluster configuration; two for the physical nodes, one for the Cluster Group name, and one for the SQL Group virtual server. Also, two private IP addresses are required for private network communications between the two nodes. Table 1 below contains the ESL cluster configuration.