Glossary
SuperLoader 3 Autoloader User’s Guide
183
O
overhead
Command overhead refers to the processing time required by
the controller, host adapter, or drive prior to the execution of a
command. Lower command overhead yields higher drive
performance.
overwrite
To write data on top of existing data thus erasing the original
data.
OEM
Original Equipment Manufacturer.
P
parallel channel architecture
Allows DLT tape drives to read/write
multiple channels simultaneously providing an industry-leading
data transfer rate in the DLT 7000 drive. with this architecture,
data blocks are not required to be located on any particular track
or in consecutive order. This channel-independent block
structure provides a powerful write-error handling system that
allows bad blocks to be rewritten on the next available command.
Partial Response, Maximum Likelihood
PRML. A technology that allows
a disk or tape drive’s read channel to pack more data in the same
amount of space on magnetic media.
peak transfer rate
The maximum speed with which information moves
inside a tape drive or between drive and host. Usually measured
in megabytes per second.
performance
A measure of the speed of the drive during normal
operation. Factors affecting performance are seek times, transfer
rate, and command overhead.
peripheral
A device added to a system as a complement to the basic
central processing unit (CPU), such as a disk drive, tape drive, or
printer.
POH
Power-on Hours. The unit of measurement for mean time
between failure (MTBF), expressed as the number of hours that
the drive is powered on. See MTBF.
POST
Power-on Self Test. Diagnostics programs, loaded automatically
by the BIOS, that perform basic tests on the major system
components, such as memory, cartridge and magazine
information. If no problems are detected during POST, the
system continues the start-up process.
PRML
See Partial Response, Maximum Likelihood.