HP Array Controller HSG V8.7 Software - Manual (Page 205)

Glossary
UltraSCSI RAID Enclosure Glossary–17
UltraSCSI RAID subsystem
One or more UltraSCSI RAID enclosures mounted in either a
pedestal or a cabinet. Each subsystem requires a master enclosure.
Adding one or two expansion enclosures to any single-enclosure
subsystem creates an expanded subsystem.
VHDCI
Very high density cable interconnect. A 68-pin interface cable with
connectors on 0.8 mm centers. Required for UltraSCSI operation.
warm swap
A method of device replacement whereby the complete system
remains online during device removal or insertion. During device
insertion or removal, the bus might halt for a brief period of time.
System booting or code loading cannot occur until insertion of the
replacement device. There is no noticeable impact on user
applications that are not dependent upon the devices on the affected
SCSI bus.
See also cold swap and hot swap.