Larger Clusters

Up to Four Nodes with SCSI Storage

You can configure up to four nodes using a shared F/W SCSI bus. An example of a four-node OPS cluster appears in the following figure.

Figure 2-9 Four-Node OPS Cluster

In this type of configuration, each node runs a separate instance of OPS and may run one or more high availability packages as well.

The figure shows a dual Ethernet configuration with all four nodes connected to a disk array (the details of the connections depend on the type of disk array). In addition, each node has a mirrored root disk (R and R'). Nodes may have multiple connections to the same array using alternate links (PV links) to take advantage of the array's use of RAID levels for data protection. Alternate links are further described in the section "“Creating OPS Volume Groups on Disk Arrays ”" in the chapter "Chapter 5 “Building an OPS Cluster Configuration”."

	NOTE: You cannot use a disk within a disk array as a root disk if the array is on a shared bus. You cannot use a disk in the A3231A (Model 10) or 3232A (Model 20) disk array as a cluster lock disk; disks in other types of supported disk arrays can be used as cluster locks. OPS clusters larger than two nodes must use disk arrays in RAID configurations with PV links for shared database storage. LVM mirroring with MirrorDisk/UX is not supported for shared database storage.

Up to Eight Nodes with EMC Disk Arrays

You can create a cluster of up to eight nodes if you use non-shared buses with the EMC disk array family. Each node should be connected to the array on two different SCSI or FibreChannel direct connect buses. This type of cluster is shown in the following figure.

Figure 2-10 Eight Node Cluster

The configuration shown above uses alternate links (PV links) to provide redundant access to the array from each node.