HP StorageWorks 2405 Disk System - Manual (Page 28)

28 Product Description
Definitions
The following terms have specific meanings in the context of this guide:
High availability (HA)
HA describes hardware and software systems that are designed to minimize
planned and unplanned downtime. High availability is measured at the system
level and stated as the percentage of time the system is in a state to do useful
work; for example, 99.95% availability translates to four hours of downtime per
year.
Hot-pluggable
Hot-pluggable signifies the ability of a component to be installed or replaced
without interrupting storage operations and within the restrictions of the
operating environment. All customer-replaceable disk system components can be
replaced under power. Adding or replacing disks or LCCs may require the use of
HP-UX commands to manage file systems.
JBOD
Pronounced jay-bod, a JBOD (Just a Bunch Of Disks) is an enclosed group of
disks that are addressed individually by the host.
PDU and PDRU
PDUs (power distribution units) distribute power from a single inlet to multiple
outlets. PRUs (power relay units) connect one or more PDU inlets to a single on/
off switch, such as a cabinet power switch. Units that both distribute and switch
power are referred to as PDRUs.
Short Wave
Lasers or LEDs that emit light with wavelengths around 780 nm or 850 nm. Short
wave lasers are used for Fibre Channel links up to approximately 700 m. They
are typically used with multimode fiber. The preferred fiber core size is 50
microns since this fiber has large bandwidth so the distance is limited by fiber
attenuation. A 62.5 micron core size is also supported for compatibility with
existing FDDI installations. Fiber of this type has smaller bandwidth and, in this
case, the distance is limited by fiber bandwidth.