Exabyte EXB-8505 8mm Write Operations, Data Flow and Data Compression, Functional Description

3Functional Description

Write Operations

Figure 3-1 provides a high-level overview of the tape drive’s flow of data during a write operation.

SCSI bus

1

Data not to be compressed

2

Data to be compressed

Compression

circuit

Data buffer

3

Data written to tape

4 Read-after-write

5

Rewrite (if necessary)

Tape

Figure 3-1Data flow during a write operation

Data Flow and Data Compression

The data-flow process during a write operation is outlined below. (The steps below correspond to the circled numbers in Figure 3-1.) These steps are described in further detail in the rest of this section.

①If you select uncompressed format (8200 or 8500) for the tape, the data goes directly from the SCSI bus to the tape drive’s

1-MByte DRAM data buffer. (Data transfers between the SCSI bus and the buffer occur asynchronously or synchronously.)

②If you select compressed format (8200c or 8500c) for the tape, the tape drive looks at the currently active MODE SELECT parameters to see if data compression has been turned on.

Note: If you select 8200c format, data compression is always on; you cannot turn it off.

3-2	EXB-8205 and EXB-8505	510504
	(Standard and XL)