HP A3550A - High Availability Disk Arrays Model 20 Storage Enclosure User Manual page 126

Disk Array Configurations
Configuration type
Basic
One host
One SCSI-2 adapter
One SCSI-2 bus
One SP
Two-SP
One host
One SCSI-2 adapter
One SCSI-2 bus
Two SPs
Features
With RAID of any supported level, applications can continue to run
after the failure of a single physical disk module within a logical disk
unit (LUN). Applications cannot continue to run if a SP or SCSI-2
adapter fails.
Provides the same features as the basic configuration, but with
better performance and higher availability. With RAID of any
supported level, applications can continue to run after the failure of
a single physical 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 limit is possible. If the SCSI-2 adapter fails, no I/O operations
are possible between the host and the array.
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