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3.7.1 Configuring 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 5.1 supports both
transparent failover, which occurs automatically, without host intervention,
and multiple-bus failover, which requires host intervention for some failures.
______________________ Note _______________________
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.
______________________ Note _______________________
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