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MaxNAS Owner’s Manual
73
be obtained by simply evaluating the XOR of the N bytes. Parity allows one error in a group
(of bytes) to be corrected.
Partition The space contributed to each array on a physical drive is referred to as a
partition.
PCI An acronym for “Peripheral Component Interconnect”. It is Intel’s local bus standard
that supports up to four plug-in PCI cards per bus. Since PCs can have two or more PCI
buses, the number of PCI cards they can support are a multiple of four. The current PCI
bus implementation (version 2.2) incorporates two 64-bit slots at 66 MHz. Consequently, the
highest throughput achievable using such a bus is 528 MB/sec.
PCI Express (Peripheral Component Interconnect Express) officially abbreviated as PCI-E or
PCIe, is a computer host bus interface format introduced by Intel in 2004. PCI Express was
designed to replace the general-purpose PCI expansion bus, the high-end PCI-X bus and the
AGP graphics card interface. Unlike previous PC expansion interfaces, rather than being a bus
it is structured around point-to-point serial links called lanes. Each lane is capable of 250MB/S
in each direction (PCIe 1.1) or 500MB/S in each direction (PCIe 2.0)
PCI-X An enhanced version of PCI version 2.2. It supports one PCI slot per bus when running
at 133 MHz, two slots when running at 100 MHz and four slots when running at 66 MHz.
It is intended to provide throughputs in excess of 1 GB/sec using a 64-bit wide 133 MHz
implementation.
Physical Drive A single tangible drive is referred to as a physical drive.
Primary Storage Main memory i.e., RAM is frequently referred to as primary storage.
RAID Abbreviation of Redundant array of independent disks. It is a set of disk array
architectures that provides fault-tolerance and improved performance.
RAID Type There are a number of RAID formats that are widely used. Some of the well-known
uni-level types are RAID 0, RAID 1, RAID 3, RAID 5 and RAID 6. The prevalent complex types
are RAID 10 and RAID 50. ,
RAID 0 RAID 0 utilizes simple striping, with the data being distributed across two or more
disks. No data redundancy is provided. The figure below illustrates a purely hypothetical
RAID 0 array comprised of three disks – disks A, B, and C – with four stripes – each uniquely
colored – across those disks. Advantage: Striping can improve the I/O throughput by allowing
concurrent I/O operations to be performed on multiple disks comprising the RAID 0 array.
However, this RAID type does not provide any data redundancy.
RAID 1 An array that uses a single pair of disks. Both disks in the pair contain the same
data It provides the best data protection but can’t improve system performance. And storage
space for the same data capacity should be double than in general cases. Hence storage cost
doubles. The capacity of RAID 1 will be the size of the smaller HDD, so we suggest you
connect HDDs of the same sizes to save HDD space. Advantage: RAID 1 ensures that if one
E-Glossary