Exabyte EXB-8505 8mm manual Track and Block Counts

2 Recording Format

Track and Block Counts

The number of tracks and physical blocks on the tape depend on the following markers:

Physical beginning of tape (PBOT). PBOT is located at the point on the tape where the translucent leader material is attached to the media. This position is detected by an optical sensor in the tape transport mechanism.

Logical beginning of tape (LBOT). When you issue a write operation at the beginning of tape, the tape drive automatically records LBOT at approximately 29 inches (74 cm) from PBOT. The LBOT area includes tracks of LBOT information, which are used to indicate the LBOT’s location, to calibrate the servo system and to indicate whether the tape was written in uncompressed or compressed format. The data contained in the LBOT blocks cannot be altered or accessed by the user.

Logical end of tape (LEOT). LEOT is determined by the number of recorded tracks that occur after LBOT. For this purpose, lengths of erased segments are converted into an equivalent number of tracks.

Physical end of tape (PEOT). PEOT is located at the point on the tape where the translucent trailer material is attached to the media. This position is detected by an optical sensor in the tape transport mechanism.

The number of tracks between LBOT and LEOT depends on the type and length of tape. Table 2-3and Table 2-4list the following information for tapes written in various formats:

The number of tracks and 1,024-byte physical blocks between

LBOT and LEOT

The approximate number of tracks and 1,024-byte physical blocks that occur between LEOT and PEOT

May 1994	EXB-8205 and EXB-8505	2-19
	(Standard and XL)