Dell 6 series User Manual page 147

Online Capacity Expansion
Operation to add capacity to an existing virtual disk by adding an additional
physical disk while the host system is active, and without affecting data
availability.
Operating Environment
An operating environment can include the host system where physical disks are
attached, any I/O buses and controllers, the host operating system and any
additional software required to manage the virtual disk. 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.
P
Parity
An extra bit added to a byte or word to reveal errors in storage (in RAM or disk)
or transmission. Parity is used to generate a set of redundancy data from two or
more parent data sets. The redundancy data can be used to rebuild one of the
parent data sets. However, parity data does not fully duplicate the parent data
sets. In RAID, this method is applied to entire physical disks or stripe elements
across all physical disks in a virtual disk. Parity consists of dedicated parity, in which
the parity of the data on two or more physical disks is stored on an additional
physical disk, and distributed parity, in which the parity data are distributed among
all the physical disks in the system. If a single physical disk fails, it can be rebuilt
from the parity of the applicable data on the remaining physical disks.
Partition
A logical structure on a contiguous segment of storage on a physical disk or
virtual disk recognized by an operating system.
Patrol Read
A preventive measure that includes review of your system for possible physical
disk errors that could lead to drive failure and damage data integrity. The Patrol
Read operation can find and possibly resolve any potential problem with
physical disks prior to host access. This can enhance overall system performance
because error recovery during a normal I/O operation may not be necessary.
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Glossary