Using Serviceguard Extension for RAC, 6th Edition, April 2008

Figure 1-5 Four-Node RAC Cluster
In this type of configuration, each node runs a separate instance of RAC 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 RAC Volume Groups on Disk Arrays ” (page 103).
Point to Point Connections to Storage Devices
Some storage devices allow point-to-point connection to a large number of host nodes
without using a shared SCSI bus. An example is shown in Figure 1-6, a cluster consisting
of eight nodes with a FibreChannel interconnect. (Client connection is provided through
Ethernet.) The nodes access shared data on an HP StorageWorks XP series or EMC disk
32 Introduction to Serviceguard Extension for RAC