Seagate STT8000A manual Tape reference servo pattern, Blocks

Chapter 6 Tape format

Blocks

Information in the Block Control byte determines the type of block being recorded except for ECC blocks which are recognized by their block numbers. Also, information about the number of user data bytes available in each data block is recorded in the Block Control byte of the block.

The Data Field of the blocks always contain 512 bytes. However, the number of valid data bytes in the block may be less than 512.

The seven different types of blocks are as follows:

∙Data blocks contain user data. A full Data block contains 512 bytes; however, data block can contain from 1 through 511 valid data bytes depending on the selected logical block size of the host.

∙Media Header blocks contain specific host., drive, and vendor information as well as the Volume Directory. The first frame on the Directory Track is teh Media Header Frame. This frame contains 52 Media Header blocks (plus the normal 12 ECC blocks).

∙Information blocks—Filemark blocks, Setmark blocks, and Cancelmark blocks—contain specific types of information. Filemark blocks are physical blocks written to tape in response to a host WRITE FILEMARKS command. Setmark blocks are physical blocks written to tape in response to a host WRITE SETMARKS command. Cancelmark blocks are physical blocks written to tape under firmware control.

∙Filler blocks contain no valid information in the data area. These blocks are used to fill incomplete frames.

∙EOD blocks are absolute indicators of the end of recorded data.

∙ECC blocks contain error correction parity bytes that are used to ensure data integrity during read operations.

∙Track ID blocks are recorded as part of the pre-formatting process of the cartridge.

Tape reference servo pattern

To increase track density, a track servo reference pattern is prerecorded on the tape at the factory. The pattern is recorded referenced to servo patterns in the region between the beginning-of-tape (BOT) hole and the load point market (LP) hole. The same pattern is recorded between the end-of-tape (EOT) hole and the early warning (EW) hole. The servo pattern is written across the entire width of the tape.

Page 66 STT8000A Product Manual