Compaq ProLiant 6500 Compaq Parallel Database Cluster Model PDC/05000 for Orac - Page 59
I/O Path Configuration Examples for Redundant FCALs, Dual Redundancy Configuration Example
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Cluster Architecture 2-35 While cluster nodes use the unit number (Dxxyy) to identify and access a storageset or a single disk drive unit in the shared storage subsystems, the array controllers use a Port-Target-LUN (PTL) address to identify and access these resources in their storage subsystem. For the MA8000/EMA12000 Storage Subsystem, the PTL address contains the following information: I The SCSI port number (1-6) identifies the disk enclosure in which the target physical disk drive is located. I The target ID number (0-5 and 8-15) of the device identifies the physical disk drive. I The LUN of the device (for disk devices, the LUN is always 0). I/O Path Configuration Examples for Redundant FC-ALs Every I/O path connection between host adapters and array controller ports is active at the same time. An active port does not become inactive unless it fails, whereupon all I/O activity on the failed path is automatically switched over to the pre-defined backup I/O path. Dual Redundancy Configuration Example In a redundant FC-AL, a dual redundancy configuration is the minimum allowable configuration that provides redundancy along the I/O paths. This configuration provides two of each component along the I/O paths. These include at least two nodes, two host adapters in each node, and two Storage Hubs. Figure 2-16 shows the correct method for cabling the I/O path components in a dual redundancy configuration. In this example, both Storage Hubs connect to port 1 on one array controller and to port 2 on the other array controller in each MA8000/EMA12000 Storage Subsystem. If one Storage Hub fails, the other Storage Hub still has access to port 1 on one array controller and port 2 on the other array controller in each storage subsystem. This ensures that the host adapters can still access the full range of LUNs.