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Chapter 2: Storage System Configurations
In this example, if one SP or SCSI-2 interface fails, stored data in either LUN
is available through the alternate path. Automatic path switching in the
event of an SP or SCSI-2 interface failure is possible if XLV volumes and
applicable patches are used. For information on XLV volumes, see Getting
Started With XFS Filesystems.
Note:
Only qualified Silicon Graphics System Service Engineers can replace
SPs or SCSI-2 interfaces.
Split-Bus Configuration
The split-bus configuration has two hosts, each with a SCSI-2 interface
connected by a SCSI-2 bus to a storage-control processor in the storage
system. Each host uses its own disks in the storage system independently.
The split-bus configuration resembles two basic configuration systems side
by side. This configuration can be used for sites requiring high availability
because either host can continue after failure of any disk module within a
disk array, and a host can take over a failed host’s disks. A host cannot
continue after a SCSI-2 interface or an SP fails unless you manually transfer
disk ownership.
Table 2-4 lists the error recovery features for this configuration.
Table 2-4
Error Recovery: Split-Bus Configuration
Failing Component
Continue After
Failure?
Recovery
Disk module
Yes
Applications continue running. System operator replaces
module.
Storage-control
processor
Yes
I/O operations fail to disk units owned by a failing SP. System
operator can transfer control of failed SP’s disk units to the
working SP, shut down the host, power off and on the storage
system, and reboot the host. Silicon Graphics SSE or other
authorized service provider replaces the SP and transfers
control of disk units to the replacement SP.
Fan module
Yes
Applications continue running. Silicon Graphics SSE or other
authorized service provider replaces the module.
