HP NetRAID 1 Controller - Manual (Page 81)

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Initialization: The process of writing zeros to the data fields of a logical drive and generating
corresponding parity to put the logical drive in a Ready state. Initializing erases previous data,
generating parity so that the logical drive will pass a Consistency Check. Arrays will work without
initializing, but they may fail a Consistency Check because parity fields may not have been
generated.
I/O Driver: A host NetServer software component (usually part of the operating system) that
controls the operation of peripheral adapters or adapters attached to the host NetServer. I/O drivers
communicate between applications and I/O devices, and in some cases participates in data transfer.
Logical Drive: A virtual drive within an array, which may consist of more than one physical drive.
Logical drives divide up the contiguous storage space of an array of disk modules or a spanned
group of arrays of disks. The storage space in a logical drive is spread across all the disks in the
array or spanned arrays. Each HP NetRAID adapter can be configured with up to eight logical drives
in any combination of sizes. Configure at least one logical drive for each array.
A logical drive can be in one of three states (also see the SCSI Disk Status below):
•
Online: all participating disk modules are online.
•
Degraded: (Critical) a single disk module in a redundant array (not RAID 0) is not online.
Data loss may result if a second disk module fails.
•
Offline: two or more disk modules in a redundant array (not RAID 0) or one or more disk
modules in a RAID 0 array are not online.
I/O operations can only be performed with logical drives that are online or degraded (critical).
Logical Volume: An array virtual disk made up of logical disks rather than physical ones. Also
called a partition.
Mapping: The conversion between multiple data addressing schemes, especially conversions
between member disk block addresses and block addresses of the virtual disks presented to the
operating environment by Array Management Software.
MB: A megabyte; an abbreviation for 1,048,576 (2 to the 20th power) bytes; used for memory or
disk capacities.
Multi-threaded: Having multiple concurrent or pseudo-concurrent execution sequences in computer
systems. Multi-threaded processes allow throughput-intensive applications to efficiently use a disk
array to increase I/O performance.
ns: A nanosecond, 10^-9 seconds.
Online: Information available via any medium (e.g., disk, CD-ROM, network) that is accessible by
computer, as opposed to hardcopy.
Online Expansion: Capacity expansion by adding volume or another hard drive.
Operating Environment: The operating environment includes the host computer where the array is
attached, any I/O buses and adapters, the host operating system, and any additional software required
to operate the array. For host-based arrays, the operating environment includes I/O driver software
for the member disks, but does not include Array Management Software, which is regarded as part
of the array itself.
Parity: Parity is an extra bit added to a byte or word to reveal errors in storage (in RAM or disk) or
transmission. It is used to generate a set of redundancy data from two or more parent data sets. The
redundancy data can be used to reconstruct one of the parent data sets; however, parity data do not
fully duplicate the parent data sets. In RAID, this method is applied to entire drives or stripes across
all disk drives in an array. Parity consists of Dedicated Parity, in which the parity of the data on two
or more disks is stored on an additional disk, and Distributed Parity, in which the parity data are