Exabyte EXB-8205 Instruções de Operação descarregar pdf (Página 77)

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3.5 Using Filemarks and Setmarks

Filemarks and setmarks enable an initiator to locate particular blocks

of data using high-speed search. When writing data to tape, an

initiator can use WRITE FILEMARKS commands to write filemarks or

setmarks (8500c format only) to indicate data boundaries. When

reading the tape, the initiator can use a SPACE command to position

the tape to data marked by a filemark at 75 times the normal tape

speed (or 10 times the normal tape speed when reading an 8200

format tape). Setmarks (8500c format only) provide an additional

way to indicate data boundaries on the tape; in a sense, they can be

thought of as a “hierarchically superior” filemark.

Filemarks

The CTS supports both short and long filemarks. The sizes of these

filemarks are different in the various data formats, as described below.

Long Filemarks—8500c and 8500 Formats

The long filemark in 8500c and 8500 formats consists of six tracks of

information:

Two tracks of erase gap at the beginning

Two tracks of long filemark physical blocks

Two tracks of erase gap at the end

Long Filemarks—8200c and 8200 Formats

The long filemark in 8200c and 8200 formats consists of 270 tracks of

information:

249 tracks of erase gap at the beginning

21 tracks (168 blocks) of long filemark physical blocks

Short Filemarks—8500c, 8500, and 8200c Formats

The short filemark in 8500c, 8500, and 8200c formats consists of a

single 1-KByte physical block.

Short Filemarks—8200 Format

The short filemark in 8200 format consists of 23 tracks of information:

2 tracks of erase gap

21 tracks of short filemark physical blocks

May 1994 EXB-8205 and EXB-8505

(Standard and XL)

3-15

3 Implementing CTS Operations

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Exabyte EXB-8205 Instruções de Operação Página 77

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