APM_level的全称为Advanced Power Management level,即(硬盘)高级电源管理级别.
man hdparm 可见:
Get/set Advanced Power Management feature, if the drive supports it.
A low value means aggressive power management and a high value means better performance.
Possible settings range from values 1 through 127 (which permit spin-down), and values 128 through 254 (which do not permit spin-down).
The highest degree of power management is attained with a setting of 1, and the highest I/O performance with a setting of 254.
A value of 255 tells hdparm to disable Advanced Power Management altogether on the drive (not all drives support disabling it, but most do).
该值的取值范围为1~255,值越大,硬盘性能越高,其中255表示关闭硬盘/dev/sda的电源管理,254表示在开启电源管理下的最高性能,1表示最低的硬盘性能但最省电.
这个值在1~127区间时允许spin-down,在128~254这个区间则禁止spin-down.
spin-down是指在闲置时挂起硬盘,停止转动,但是频繁的spin-down和spin-up会使硬盘寿命变短.
所以,即使你追求节能,减少发热量,也建议你将该值设为128,执行以下命令即可:
注意: 设置APM后执行以下命令查看Load_Cycle_Count值
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