HP Surestore Disk Array 12h - And FC60 Advanced User's Manual page 450

NVSRAM
The disk array controller stores operating configuration information in this non-volatile
SRAM (referred to as NVSRAM). The contents of NVSRAM can only be accessed or
changed using special diagnostic tools.
path
See primary disk array path or primary path.
parity
A data protection technique that provides data redundancy by creating extra data based
on the original data. Parity is calculated on each write I/O by doing a serial binary
exclusive OR (XOR) of the data segments in the stripe written to the data disks in the
LUN. Parity is used by RAID 5 LUNs to reconstruct data from a failed disk.
peripheral device addressing (PDA)
The addressing technique used by the host to address the disk array controllers.
Because it is limited to addressing only eight LUNs, PDA has been superseded by VSA
as the technique for addressing disk array LUNs.
point-to-point
One of three existing Fibre Channel topologies, in which two devices are directly
connected by a link with no fabric, loop, or switching elements present.
port
The hardware entity that connects a device to a Fibre Channel topology. A device can
contain one or more ports.
primary disk array path or primary path
The main data path used for host I/Os to a LUN. The primary path can be set using LVM.
Because the disk array has two controllers, one controller acts as the primary path, and
the other acts as the alternate path. If a failure occurs in the primary data path, the
alternate path is used, maintaining access to the LUN.
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