Glossary

SCSI BUS – A multi-signal parallel bus that interconnects SCSI devices in a daisy-chain fashion.

SCSI DEVICE – A host adapter or a target controller that can be attached to the SCSI bus.

SCSI ID – The bit-significant representation of the SCSI address referring to one of eight (or one of sixteen) data lines.

SECTOR – On a PC hard drive, the minimum segment of track length that can be assigned to store information. On Macintosh and UNIX drives, sectors are usually grouped into blocks or logical blocks that function as the smallest data unit permitted. Since these blocks are often defined as a single sector the terms block and sector are sometimes used interchangeably in this context. (Note: The usage of the term block in connection with the physical configuration of the disk is different from its meaning at the system level. See also block and cluster for comparison.)

SEEK – A movement of the disk read/write head to a specific data track.

SEGMENTED CACHE BUFFER – A cache buffer that is organized into multiple track lines. Segmenting the cache allows track data to be saved in separate segments when the head is switched rather than having to erase the entire cache. Segmenting the cache enables command reordering on a more efficient track-basis rather than on a command-basis.

SENSE DATA – Information returned to an initiator regarding error conditions in the drive.

SERVO SECTOR TIME – The time (in µsec) between reading one servo header (or “spoke”) and reading the next header.

SERVO SPOKE DATA – In embedded servo technology, digital and quadrature analog servo data is written (embedded) in multiple headers (or “spokes”) on each track on the data- recording area of each disk surface. The digital portion of the spoke data are read and used to locate the correct track, spoke, and head number. The quadrature analog signal portion is detected and used by a servo feedback control loop to precisely position the head on the track

center.

SERVO DATA – Magnetic markings written on the media that guide the read/write heads to the proper position.

SERVO SURFACE – A separate surface containing only positioning and disk timing information but no data.

SETTLE TIME – The interval between the arrival of the read/write head at a specific track, and the lessening of the residual movement to a level sufficient for reliable reading or writing.

SHOCK RATING – A rating, expressed in “G’s”, of how much shock a disk drive can sustain without damage.

SIGNAL ASSERTIOn – The act of driving a signal to the true (logical-one) state. An asserted signal on the SCSI bus is a low voltage resulting from driving a transistor ON.

SIGNAL NEGATION – The act of driving a signal to the false (0) state, or allowing the cable terminators to bias the signal to the false state by placing the data driver in the high impedance (off) condition. A negated signal on the SCSI bus is a high voltage resulting from all OR-tied transistors being OFF.

SIGNAL RELEASE – The act of allowing the cable terminators to bias the signal to the false state by placing the bus driver in the high impedance (off) condition.

SINGLE-ENDED TERMINATION – One of two methods for terminating the SCSI bus, characterized by signal values that conform to the ANSI-defined levels for SCSI implementation. Typically used for short cable runs. See also differential termination.

SKEW – To shift sector addresses when switching tracks or cylinders to create a slight overlap under the read/write heads. The overlap works to delay the arrival of the next (in sequence) sector from arriving under the selected head until the track or cylinder switch has been done. Skewing minimizes latency time (increasing data throughput) when data on the drive is accessed sequentially.

G-10Maxtor Atlas 10K V