Exabyte EXB-8505 8mm manual Search Fields, Servo Areas

2Recording Format

Search Fields

For 8500/8500c and 8200c track structures, each track contains search fields used for high-speed search. (Figure 2-8 shows where search fields are located in a track.) The search fields are the only areas of the tape that are read during a high-speed search. The search field data contains information for locating files and blocks and detecting the end-of-data (EOD) mark during high-speed searches.

Note: Tapes written in 8200 format are SCSI-1 compatible and do not contain search fields. For this reason, 8200 format tapes do not support high-speed search. In addition, the EXB-8205, EXB-8205XL, EXB-8505, and EXB-8505XL do not support the EXB-8200SX high-speed search feature.

Servo Areas

For all three physical track structures, each track contains servo areas that the tape drive uses to read tapes written by other tape drives. Each servo area contains a signal that the servo head detects and uses to control linear tape velocity. This track-following servo process results in accurate positioning of the track under the read head.

The servo scheme is based on the geometry of the track positions. Each servo area consists of one servo data signal burst surrounded by an erase (margin) signal. The tape drive places servo areas in the following locations, based on physical track format:

In 8200 format, the tape drive places a servo area at the beginning of each track (as shown in Figure 2-6).

In 8200c format, the tape drive places a servo area at the beginning, middle, and end of every track (as shown in Figure 2-7).

In 8500/8500c format, the tape drive places a servo area at the beginning, middle, and end of every other track (as shown in Figure 2-4).

Note: Refer to the EXB-8200 8mm Cartridge Tape Subsystem Product Specification for information about track-following servo for 8200 format.

2-10	EXB-8205 and EXB-8505	510504
	(Standard and XL)