Fujitsu MHW2040BS Product Manual page 280

Glossary
DE
Disk enclosure. The DE includes the disks, built-in spindle motor, actuator, heads,
and air filter. The DE is sealed to protect these components from dust.
Host receptacle
Host receptacle is a connector type on the host system that the signal segment of
Serial-ATA unifies with the power supply segment.
Master (Device 0)
The master is the first drive that can operate on the AT bus. The master is daisy-
chained with the second drive which can operate in conformity with the ATA
standard.
MTBF
Mean time between failures. The MTBF is calculated by dividing the total
operation time (total power-on time) by the number of failures in the disk drive
during operation.
MTTR
Mean time to repair. The MTTR is the average time required for a service person
to diagnose and repair a faulty drive.
PIO (Programmed input-output)
Mode to transfer data under control of the host CPU
Positioning
Sum of the seek time and mean rotational delay
Power save mode
The power save modes are idle mode, standby mode, and sleep mode.
In idle mode, the drive is neither reading, writing, nor seeking data. In standby
mode, the spindle motor is stopped and circuits other than the interface control
circuit are sleeping. The drive enters sleep mode when the host issues the SLEEP
command.
Reserved
Reserved bits, bytes, and fields are set to zero and unusable because they are
reserved for future standards.
Rotational delay
Time delay due to disk rotation. The mean delay is the time required for half a
disk rotation. The mean delay is the average time required for a head to reach a
sector after the head is positioned on a track.
GL-2 C141-E249