Maxtor manual 8Maxtor Atlas 10K III 18/36/73 GB Ultra160 Scsi

Glossary

PERIPHERAL – A device added to a system as an enhancement to the basic CPU, such as a disk drive, tape drive or printer.

PHYSICAL FORMAT – The actual physical layout of cylinders, tracks, and sectors on a disk drive.

PHYSICAL SECTOR –See sector, data.

PLATTER – Common term referring to the hard disk.

POH – Power On Hours. The unit of measurement for Mean Time Between Failure as expressed in the number of hours that power is applied to the device regardless of the amount of actual data transfer usage. (See also MTBF.)

POSITIONER – See actuator.

PREFETCH –The technique of buffering data into cache RAM by reading subsequent blocks in advance to anticipate the next request for data. Prefetch speeds up disk accesses to sequential blocks of data.

PRML – Partial-Response Maximum- Likelihood. A sophisticated data-detection method that improves data throughput and increases areal density. PRML read channels are used in place of peak-detection read channels.

QUEUE – A prioritized!list or set of processes.

Aqueue may be a FIFO (first-in, first-out), LIFO (last-in, first -out) or a random-access entity.

QUEUE TAG – The value associated with an I/O process that uniquely identifies it from other queued I/O processes in the logical unit from the same initiator.

QUEUED I/O PROCESS – An I/O process that is in the command queue.

RAM – Random Access"Memory. An integrated circuit memory chip that allows information to be stored and retrieved by a microprocessor or controller. The information may be stored and retrieved in any order, and all storage locations are equally accessible.

RAM DISK – A “phantom” disk drive created by setting aside a section of RAM as if it were a group of regular sectors. Access to RAM disk data is extremely fast, but is lost when the system is reset or turned off.

READ – The function of detecting, processing and transmitting data that has been recorded (written) on a magnetic disk or some other media.

READ AFTER WRITE – A mode of operation requiring that the system read each sector after data is written, checking that the data read back is the same as the data recorded. This operation lowers system speed but raises data reliability.

READ VERIFY – A data accuracy check performed by having the disk read data to the controller, which then checks for errors but does not pass the data on to the system.

READ/WRITE HEAD – The tiny electromagnetic coil and metal pole piece used to create and read back the magnetic patterns (write or read information) on the disk. Each side of each platter has its own read/write head.

RECONNECT – The act of reviving a nexus to continue an I/O process. An initiator reconnects to a target using the SELECTION and MESSAGE OUT phases after winning arbitration. The target reconnects to the initiator using RESELECTION and MESSAGE IN phases after winning arbitration.

RECONNECTION – The state which results from a reconnect. It exists from the assertion of BSY in the SELECTION or RESELECTION phase and lasts until the next BUS FREE phase.

REMOVABLE DISK – Generally said of disk drives where the disk itself is meant to be removed, and in particular of hard disks using disks mounted in cartridges. Their advantage is

G-8Maxtor Atlas 10K III 18/36/73 GB Ultra160 SCSI