HP A3550A - High Availability Disk Arrays Model 20 Storage Enclosure User Manual page 110

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
Provides highest availability and best array performance for single-
host configurations. Applications can continue to run after failure of a
disk module.
HP-UX 9.04
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 by way of LVM. Once these changes have been made,
access to all LUNs on the array 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
need to be reassigned by using Grid Manager and LVM, respectively.
HP-UX 10.x
If one SP fails, ownership of the failed SP's LUNs can transfer
automatically to the remaining operational SP. If a primary and an
alternate path have been configured in LVM, LVM switches
automatically to the alternate path. If the SCSI-2 adapter fails,
transfer of LUN ownership and the LVM switch to the alternate path
take place automatically. These operations are transparent to the
user.
Resembles two basic configurations side-by-side, and provides
modest high availability with the external SCSI-2 bus not shared
between two hosts. Applications can continue to run after a disk
module failure.
HP-UX 9.04
There is no automatic transfer of LUN ownership or path for this
configuration type.
HP-UX 10.x
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 LVM and Grid
Manager, respectively.
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