IBM 201 manual PCI see Peripheral Component Interconnect, PCNFSD see personal-computer NFS daemon

optical cable. A fiber, multiple fibers, or a fiber bundle in a structure built to meet optical, mechanical, and environmental specifications (E).

optical fiber. Any filament made of dielectric materials that guides light, regardless of its ability to send signals.

optical fiber coupler. (1) A device whose purpose is to distribute optical power among two or more ports (A). (2) A device whose purpose is to couple power between a fiber and a source or detector (A).

P

packet internet groper (PING). In Internet communications, a program used in TCP/IP networks to test the ability to reach destinations by sending the destinations an Internet Control Message Protocol (ICMP) echo request and waiting for a reply.

parity check. (1) A redundancy check by which a recalculated parity bit is compared to the pre-given parity bit (T).

(2) A check that tests whether the number of ones (or zeros) in an array of binary digits is odd or even (A).

passive hub. A hub that adds nothing to the data being transmitted through it.

path. The connection between a storage port and the WWN (World Wide Name): target : LUN of a storage device.

path group. A collection of equivalent paths. Storage devices may have one, two or n path groups.

PCI (see Peripheral Component Interconnect).

PCNFS (see personal-computer network file system).

PCNFSD (see personal-computer NFS daemon).

PCMCIA (see Personal Computer Memory Card International Association).

PDC (see primary domain controller).

PDU. Power distribution unit.

Peripheral Component Interconnect (PCI). A local bus for PCs from Intel that provides a high-speed data path between the CPU and up to 10 peripherals (video, disk, network, and so on). The PCI bus coexists in the PC with the ISA or EISA bus. ISA and EISA boards still plug into an ISA or EISA slot, while high-speed PCI controllers plug into a PCI slot.

Persistent Storage Manager (PSM). Columbia Data Products software that creates multiple point-in-time persistent True Image data views of any or all system and data volumes residing on the NAS. All persistent images survive system a power loss or a planned or unplanned reboot. Each instance of PSM seamlessly handles 250 concurrent images of up to 255 independent volumes for a total of 63,750 independent data images.*

personal-computer NFS daemon (PCNFSD). A daemon that manages user authentication and print spooling.

Personal Computer Memory Card International Association (PCMCIA). An organization that standardizes credit-card size memory and I/O adapters for personal computers.

PING (see packet internet groper).

pinout. Information that specifies which signal, signal line, or cable wire maps to each pin on a module, card, or cable connector. A module is usually keyed to allow for pin number identification.

PPS (see per port switching).

primary adapter. In a personal computer that is used on a LAN and that supports installation of two network adapters, the adapter that uses standard (or default) mapping between adapter-shared RAM, adapter ROM, and designated computer memory segments. The primary adapter is usually designated as adapter 0 in configuration parameters. Contrast with alternate adapter.

promiscuous mode. In a local area network (LAN), a method of processing and monitoring LAN frames that does not discriminate based on address.

IBM Glossary of Storage Networking Terms 119