Exabyte EXB-8505 8mm manual Gap Bytes, 10Gap bytes one physical block

2 Recording Format

Gap Bytes

A gap byte is a byte containing undefined data that the tape drive uses to fill empty space in a physical block. The tape drive may automatically write gap bytes in the following cases:

At the end of a write operation.

Before writing a filemark.

Before writing a setmark (EXB-8505 or EXB-8505XL only).

When it is physically impossible to start the next logical block in the physical block because less than three bytes are available. (This is because the two-byte header and at least one data byte must be present in the first physical block before the logical block can spill over to a second physical block.)

Figure 2-10 shows how gap bytes can be used to fill empty space at the end of a physical block. Gap bytes cannot be accessed by any SCSI command.

Header, 2 logical blocks, header, 2 logical blocks, and 2 gap bytes

256 bytes

256 bytes

256 bytes

250 bytes

14-byte header 2-byte headers 2 gap bytes

Figure 2-10Gap bytes (one physical block)

May 1994	EXB-8205 and EXB-8505	2-15
	(Standard and XL)