Compaq AA-RHGWB-TE manual

3.7.1Configuring Radially Connected TruCluster Server Clusters with UltraSCSI Hardware

Radial configurations with RAID array controllers allow you to take advantage of the benefits of hardware mirroring, and to achieve a no-single-point-of-failure (NSPOF) cluster. Typical RAID array storage subsystems used in TruCluster Server cluster configurations are:

•RA7000 or ESA10000 with HSZ70 controller

•RA7000 or ESA10000 with HSZ80 controller

•RA8000 or ESA12000 with HSZ80 controller

When used with TruCluster Server, one advantage of using a RAID array controller is the ability to hardware mirror the clusterwide root (/) file system, member system boot disks, swap disk, and quorum disk. When used in a dual-redundant configuration, Tru64 UNIX Version 5.0A supports both transparent failover, which occurs automatically, without host intervention, and multiple-bus failover, which requires host intervention for some failures.

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Enable mirrored cache for dual-redundant configurations to further ensure the availability of unwritten cache data.

Use transparent failover if you only have one shared SCSI bus. Both controllers are connected to the same host and device buses, and either controller can service all of the units if the other controller fails.

Transparent failover compensates only for a controller failure, and not for failures of either the SCSI bus or host adapters and is therefore not a NSPOF configuration.

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Set each controller to transparent failover mode before configuring devices (SET FAILOVER COPY = THIS_CONTROLLER).

To achieve a NSPOF configuration, you need multiple-bus failover and two shared SCSI buses.

You may use multiple-bus failover (SET MULTIBUS_FAILOVER COPY = THIS_CONTROLLER) to help achieve a NSPOF configuration if each host has two shared SCSI buses to the array controllers. One SCSI bus is connected to one controller and the other SCSI bus is connected to the other controller. Each member system has a host bus adapter for each shared SCSI bus. The load can be distributed across the two controllers. In case of a host adapter

Shared SCSI Bus Requirements and Configurations Using UltraSCSI Hardware 3–17