Dell PowerEdge 5/E, Руководство пользователя

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Glossary
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.
PHY
The interface required to transmit and receive data
packets transferred across the serial bus.
Each PHY can form one side of the physical link in a
connection with a PHY on a different Dell-qualified
SATA device. The physical link contains four wires
that form two differential signal pairs. One differential
pair transmits signals, while the other differential pair
receives signals. Both differential pairs operate
simultaneously and allow concurrent data transmission
in both the receive and the transmit directions.
Physical Disk
A non-volatile, randomly addressable device for
storing data. Physical disks are rewritable and
commonly referred to as disk drives.
Physical Disk States
A physical disk can be in one of the following states:
• Un-configured Good: A disk accessible to the
RAID controller but not configured as a part of a
virtual disk or as a hot spare.
• Hot Spare: A physical disk that is configured as a hot
spare.
• Online: A physical disk can be accessed by the
RAID controller and will be part of the virtual disk.
• Rebuild: A physical disk to which data is being
written to restore full redundancy for a virtual disk.
Dell_PERC5_UG.book Page 104 Tuesday, February 13, 2007 6:02 PM