Installation guide

Glossary
Manual No. 771961 G-5
redundancy features of the controller are used), system service continues
without interruption. A message is generated by the system to alert the
system operator.
When a replacement drive becomes available, the system operator can
remove the failed disk drive, install a new disk drive, and instruct the
controller to “rebuild” the data on the new drive, all without interrupting
system operations.
Once the rebuild is complete, the controller will be brought back into a fault
tolerant state.
IBBU
See “Intelligent Battery Backup Unit” .
Intelligent Battery Backup Unit
The Intelligent Battery Backup Unit (IBBU) is an add-on module that
provides power to a compatible PCI to Ultra-SCSI or External RAID
Controller cache memory in the event of a power failure. The battery backup
module monitors the write back cache on the controller, and provides power
to the cache if it contains data not yet written to the drives when power is
lost.
A PCI to Ultra-SCSI RAID controller, with the IBBU installed, together
occupy only one PCI slot on the host backplane.
LUN
See “Logical Unit Number (LUN)” .
LUN Mapping
External RAID Controller (Firmware 5.x and below) LUN Mapping allows
logical drives (or system drives) to be made available or unavailable on one
or more host ports. The mapping is performed by assigning Logical Unit
Numbers (LUNs) to logical drives. The LUN assignments are per host port
and are independent of the assignments on other host ports. Logical drives
may be assigned only one LUN per host port.