HP A3550A - High Availability Disk Arrays Model 20 Storage Enclosure User Manual page 127

Two-adapter/Two SP
One host
Two SCSI-2 adapters
Two SCSI-2 buses
Two SPs
Multi-bus
Two hosts
Two SCSI-2 adapters
(one per host)
Two SCSI-2 buses
(one per host)
Two SPs
5-4
Provides highest availability and best array performance for single-
host configurations. With RAID of any supported level, applications
can continue to run after failure of a disk module.
If one SP fails, the System Administrator must reassign ownership
of the failed SP's LUNs to the operational SP by using Grid
Manager. Also, the path to the operational SP must be used and
can be changed with SYSGEN or ioconfig. Once these changes
have been made, access to all LUNs on the array within the SCSI
LUN limits is possible. If the SCSI-2 adapter fails, the System
Administrator can access the array through the operational SCSI-2
adapter's path. LUN ownership and path changes must be
reassigned by using Grid Manager and SYSGEN/ioconfig.
Resembles two basic configurations side-by-side and provides
modest high availability with the SCSI-2 buses not shared between
two hosts. With MPE/iX supported RAID levels, applications can
continue to run if a disk module fails.
If one SP fails, the System Administrator can access the LUNs
owned by the failed SP by accessing the remaining operational SP
with the other host. If a host adapter fails, the System Administrator
can access the LUNs in the array with the other host adapter. The
System Administrator must change the path and the SP ownership
of the LUNs for the failed SP or failed host adapter by using SYS-
GEN/ioconfig and Grid Manager, respectively.