Exabyte EXB-8205 Instruções de Operação descarregar pdf (Página 82)

Motion Threshold

The motion threshold is used in start/stop mode to control data

transfers between the buffer and the tape. The motion threshold is

measured in 4-KByte increments. The default is 80h (512 KBytes).

This value represents half the capacity of the CTS’s buffer. You can

change the motion threshold value with a MODE SELECT (15h)

command.

Write Operations During a start/stop write operation, the motion

threshold represents the minimum amount of data that must be in

the CTS’s 1-MByte buffer before tape motion will start and data

will be written to tape. Note that if you are using 8500c or 8200c

format, this data will be compressed. Assuming an average

compression ratio of 2:1, the motion threshold can actually

represent twice that amount of user data.

When the motion threshold is exceeded, tape motion starts. The

write-to-tape operation continues until the buffer is empty and the

tape motion stops. Tape motion does not restart until the amount

of data in the buffer once again exceeds the motion threshold or

until the buffer is flushed for some other reason (such as a reverse

tape motion command).

Read Operations During a start/stop read operation, the motion

threshold represents the minimum amount of free space that must

be in the CTS’s 1-MByte buffer before tape motion will start and

data will be read from the tape to the buffer. Note that if you are

using 8500c or 8200c format, the data being read from the tape is

compressed. Assuming an average compression ratio of 2:1, the

motion threshold can actually represent twice that amount of user

data.

When the motion threshold is exceeded, tape motion starts. The

read-from-tape operation continues until the buffer is full and the

tape motion stops. Tape motion does not restart until the amount

of free space in the buffer once again exceeds the motion

threshold.

3-20

EXB-8205 and EXB-8505

(Standard and XL)

510503

3 Implementing CTS Operations

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Exabyte EXB-8205 Instruções de Operação Página 82