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Glossary 145
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.
Dell_PERC6.1_UG.book Page 145 Wednesday, April 15, 2009 4:18 PM