Exabyte EXB-8505 8mm manual Thresholds During a Read Operation, Motion Threshold

3Functional Description

Thresholds During a Read Operation

The motion threshold controls the starting and stopping of tape motion. The reconnect threshold controls the rate of disconnects and reconnects between the tape drive and the initiator.

Motion Threshold

In a start/stop read operation, the tape-to-buffer transfer speed is faster than the buffer-to-initiator transfer speed. In this mode of operation, the motion threshold value represents the minimum amount of free space that must be in the tape drive’s 1-MByte buffer before tape motion will start and data will be read from the tape to the buffer. The read-from-tape operation continues until the buffer is full and tape motion stops. Tape motion does not restart until the amount of free space in the buffer once again exceeds the motion threshold value.

Reconnect Threshold

In a streaming read operation, the tape-to-buffer transfer rate is equal to or less than the buffer-to-initiator transfer rate. In this mode of operation, the tape drive reads data from tape continually. When the buffer becomes empty, the tape drive disconnects from the initiator, and the initiator is free to perform other tasks.

For the tape drive to continue streaming, the initiator must begin to accept data again before the buffer is full. The reconnect threshold value represents the minimum amount of data that must be in the tape drive’s 1-MByte buffer before the tape drive will reconnect to the initiator to transfer data from the buffer. When the reconnect threshold value is exceeded, the tape drive reconnects to the initiator and data transfer resumes. The data transfer to the initiator continues until the buffer is empty.

3-8	EXB-8205 and EXB-8505	510504
	(Standard and XL)