Compaq ProLiant 6500 Compaq Parallel Database Cluster Model PDC/O2000 for Orac - Page 29
RA4000 Array Controllers, If the active RA4000 Array Controller in an RA4000/RA4100 Array fails
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Cluster Architecture 2-5 RA4000 Array Controllers To ensure redundant I/O paths, two single-port RA4000 Array Controllers are installed in each RA4000 Array or RA4100 Array. Only one array controller can be active at any given time. One array controller is configured as the active controller, and the other is the standby controller. To ensure fault tolerance of shared storage on the RA4000 Array or RA4100 Array, the two array controllers must be connected to a different Storage Hub, FC-AL Switch, or Fibre Channel SAN Switch. From the perspective of the cluster nodes, each RA4000 Array Controller is simply another device connected to one of the cluster's I/O paths. Consequently, each node sends its I/O requests to the active RA4000 Array Controller just as it would to any SCSI device. The RA4000 Array Controller receives the I/O requests from the nodes and directs them to the shared storage disks to which it has been configured. Because the array controller processes the I/O requests, the cluster nodes are not burdened with the I/O processing tasks associated with reading and writing data to multiple shared storage devices. When an RA4000/RA4100 Array and the cluster nodes to which it is physically connected are first powered on, the RA4000/RA4100 Array communicates with the nodes to identify which of its two array controller slots contains the active array controller. The array controller that is installed in the active slot is automatically assigned active status by Compaq Secure Path, without the need for any further configuration. To determine which of the two array controllers in an RA4000/RA4100 Array is currently active, find the controller on which the ninth green LED is lit; this LED identifies the active array controller. To change the active slot location, use Secure Path Manager to make the array controller in the other slot the active controller. For information about configuring the standby array controller to be active, refer to "Defining Active Array Controllers" in Chapter 5, "Installation and Configuration." If the active RA4000 Array Controller in an RA4000/RA4100 Array fails, Secure Path causes the standby controller to become the active array controller.