Technical data

devices. Either controller can continue to service all of the units if the other
controller fails.
______________________ Note _______________________
The assignment of HSZ target IDs can be balanced between the
controllers to provide better system performance. See the RAID
array controller documentation for information on setting up
storagesets.
In the configuration shown in Figure 1–6, there is only one shared SCSI bus.
Even by mirroring the clusterwide root and member boot disks, the single
shared SCSI bus is a single point of failure.
1.5.5 Creating an NSPOF Cluster
A no-single-point-of-failure (NSPOF) cluster can be achieved by:
• Using two shared SCSI buses and hardware RAID to mirror the cluster
file system
• Using multiple shared SCSI buses with storage shelves and mirroring
those file systems that can be mirrored with LSM, and by judicial
placement of those file systems that cannot be mirrored with LSM.
To create an NSPOF cluster with hardware RAID or LSM and shared SCSI
buses with storage shelves, you need to:
• Install a second Memory Channel interface for redundancy.
• Install redundant power supplies.
• Install redundant networks.
• Connect the systems and storage to an uninterruptible power supply
(UPS).
Additionally, if you are using hardware RAID, you need to:
• Use hardware RAID to mirror the clusterwide root (/), /usr, and /var
file systems, the member boot disks, quorum disk (if present), and data
disks.
• Use at least two shared SCSI buses to access dual-redundant RAID
array controllers set up for multiple-bus failover mode (HSZ70, HSZ80,
HSG60, and HSG80).
Tru64 UNIX support for multipathing provides support for multiple-bus
failover.
Introduction 1–15