临床症状为硬盘出现当当的金属碰撞声，这是磁头归位的声音，一个bug。其实不能算bug只是硬盘电源管理中一种节能功能，磁头归位后是为了硬盘停转。
Mac OS X解决办法，安装hdpam
A Mac utility for setting the power management (APM) level on SATA hard drives.
It can be used to eliminate "chirping" or "clicking when idle" noises in some HDDs.
Compatibility
OS X 10.5 or higher.
SATA hard disk with APM support.
Does not work with external USB or Firewire drives.
Documentation
Further information can be found in the usage guide：http://mckinlay.net.nz/hdapm/usage.html
Downloads
New! (Aug 25, 2012) version 1.2.
Improved support for systems with multiple drives.
Detects all APM compatible drives automatically (No need to edit .plist file for Optibays, Mac Pros, etc).
New uninstall script.
Installer Package hdapm-1.2.dmg：http://mckinlay.net.nz/files/hdapm-1.2.dmg
Source code hdapm-1.2-source.tar.gz：http://mckinlay.net.nz/files/hdapm-1.2-source.tar.gz
Linux也会出现该问题，解决办法是将hdparm -B 254 /dev/sdX加入开机脚本rc.local，将/dev/sdX设为你要更改的硬盘。
P.S.我的硬盘是日立的，官方提供一个工具ftool，可以将配置写入硬盘CMOS，这样就更彻底了。
Linux硬盘故障案例分享：http://www.linuxdiyf.com/linux/14170.html
硬盘故障时无法关机，内核直接重启：http://www.linuxdiyf.com/linux/13543.html
使用dd命令进行硬盘I/O性能检测：http://www.linuxdiyf.com/linux/13555.html
Linux硬盘速度测试的命令：http://www.linuxdiyf.com/linux/13456.html
win7下硬盘安装fedora 23：http://www.linuxdiyf.com/linux/15895.html