Mylex DAC960PG, Installation Manual

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Glossary
Manual No. 771971 Glossary-3
Hot Replacement of Disks (“Hot Swap”)
The design of the DAC960 Series controllers allows for the replacement of
failed hard disk drives without interruption of system service. In the event of
a SCSI drive failure on a properly configured system (where the data
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 DAC960PG PCI to Ultra-SCSI RAID Controller cache
memory in the event of a power failure. The battery backup module monitors
the write back cache on the DAC960PG, and provides power to the cache if
it contains data not yet written to the drives when power is lost.
The DAC960PG controller, with the IBBU installed, together occupy only
one PCI slot on the host backplane.
Logical Drive States
The state of a logical (system) drive can be either ONLINE, CRITICAL, or
OFFLINE. Notice that the same term “online” is used for both physical and
logical drives.
Online: A Logical Drive is in an “online” state if...
All of its participating SCSI drives are “online.”