Compaq ProLiant 6500 Deploying the ProLiant Cluster for NetWare 4.2 - Page 11

'HSOR\LQJ WKH 3UR/LDQW &OXVWHU IRU 1HW:DUH   NOTE: Currently, Fibre Channel Storage Hubs cannot be daisy chained, that is, hubs cannot be connected in series. Compaq Fibre Channel Array Controller One or two Fibre Channel Array Controllers, which reside in the Compaq RAID Array 4000 storage system, provide RAID and caching capabilities and provide the Fibre Channel interface to connect to the server. An important aspect of a high-availability system is fault tolerance, traditionally accomplished by implementing RAID technology. Hardware RAID is an integrated part of the Compaq Fibre Channel Array Controller, located within the Fibre Channel Array chassis. The Fibre Channel Array Controller supports RAID 0, 1, 4, and 5, as well as online capacity expansion and pre-failure notification for hard drives. In addition, the Fibre Channel Array Controller provides ECC (Error Checking and Correcting) memory for user-configurable read and write cache. The cache on the Array Accelerator is equipped with onboard rechargeable batteries, ensuring that the cached data is safe even with equipment failure or power outage. For a complete list of features and accompanying descriptions, refer to the Fibre Channel information on the Compaq website, http://www.compaq.com. Typically, a Compaq RAID Array 4000 storage system is configured with a single controller. However, for a higher level of availability, two array controllers can be configured as a redundant pair, such that one controller is a backup for the other, as described under "Redundant Fibre Channel Loop for Increased Availability," below. Compaq Fibre Channel Host Controller The host controller, available as a PCI adapter, interfaces between the server and the Fibre Channel Storage System through the fiber optic cable. At least two PCI Fibre Channel Host Controllers, one for each cluster node, are required in your Compaq ProLiant cluster. For higher availability, Fibre Channel Host Controllers can be configured in redundant pairs, such that one controller is a backup for the other, as described under "Redundant Fibre Channel Loop for Increased Availability," below. Redundant Fibre Channel Loop for Increased Availability For increased availability, a redundant Fibre Channel loop can be configured, which provides two redundant data paths between each cluster server and the Compaq RAID Array 4000 storage system. One data path is configured as the primary path and is initially active. The other data path is configured as a standby path and is initially inactive. The standby data path serves as a backup for the primary path. The redundant data path configuration requires the following additional components: • A second, standby Fibre Channel Host Controller installed in each server • A second, standby Fibre Channel Array Controller installed in the Compaq RA4000 • Recommended but not required: A second, standby storage hub with connections to the standby host controllers and to the standby array controller. Figure 4 shows an example of this configuration. 0096-0699-A