Hitachi HTS541616J9SA00 Specifications page 31

Travelstar 5K160 (SATA) Hard Disk Drive Specification
Hitachi recommends that the switch operate under control of the host system, as opposed to being
hardwired. The same recommendation is made for cover-close switches. When a hardwired switch is
turned off, emergency unload occurs, as well as the problems cited in section 5.1, "Data loss by power
off" on page 19 and section 5.2, "Write Cache" on page 19.
6.3.6.4 Test considerations
Start/stop testing is classically performed to verify head/disk durability. The heads do not land on the disk,
so this type of test should be viewed as a test of the load/unload function.
Start/Stop testing should be done by commands through the interface, not by power cycling the drive.
Simple power cycling of the drive invokes the emergency unload mechanism and subjects the HDD to
nontypical mechanical stress.
Power cycling testing may be required to test the boot-up function of the system. In this case HItachi
recommends that the power-off portion of the cycle contain the sequence specified in section 6.4.6.2,
"Required Power-Off Sequence" on page 29. If this is not done, the emergency unload function is
invoked and nontypical stress results.
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