•Number of shared SCSI buses and the storage on each shared bus
Using shared SCSI buses increases storage availability. Youcan connect
32 shared SCSI buses to a cluster member. You can use any combination
of KZPSA-BB, KZPBA-CB, or KGPSA-BC/CA host bus adapters.
In addition, RAID array controllers allow you to increase your storage
capacity and protect against disk, controller,host bus adapter, and SCSI
bus failures. Mirroring data across shared buses provides you with more
reliable and available data. You can use Logical Storage Manager (LSM)
host-based mirroring for all storage except the clusterwide root (/) file
system, the member-specific boot disks, and the swap and quorum disk.
•No single-point-of-failure (NSPOF) TruClusterServer cluster
Youcan use mirroring and multiple-bus failover with the HSZ70, HSZ80,
and HSG80 RAID array controllers to create a NSPOF TruCluster Server
cluster (providing the rest of the hardware is installed).
•Tapeloaders on a shared SCSI bus
Because of the length of the internal SCSI cables in some tape
loaders (up to 3 meters), they cannot be externally terminated with a
trilink/terminator combination. Therefore, in general, with the exception
of the TL890, TL891, and TL892, tape loaders must be on the end of the
shared SCSI bus. See Chapter 8 for information on configuring tape
devices on a shared SCSI bus.
•Youcannot use Prestoserve in a TruCluster Server cluster to cache I/O
operations for any storage device, regardless of whether it is located
on a shared bus or a bus local to a given system. Because data in
the Prestoserve buffer cache of one member is not accessible to other
member systems, TruClusterServer cannotprovide correct failoverwhen
Prestoserve is being used.
Table 4–1 describes how to maximize performance, availability,and
storage capacity in your TruCluster Server hardware configuration. For
example, if you want greater application performance without decreasing
I/O performance, you can increase the number of member systems or you
can set up additional shared storage.
Table4–1: Planning Your Configuration
To increase: You can:
Application performance Increasethe numberof membersystems.
I/O performance Increase the number of shared buses.
Member system availability Increasethe numberof membersystems.
Clusterinterconnect availability Use redundant cluster interconnects.
TruClusterServer System Configuration Using UltraSCSI Hardware 4–3