USB disk 卸載之安全考量

道德經:	致虛極，守靜篤。萬物並作，吾以觀復。

The Safe Removal just means a software safely protect buffer/cache to USB disk instead of when suddenly unplug the disk from the USB port, by handling the important things of “sync”, “shutdown” and “un-mount” procedures. Despite we don’t have a grayed soft panel icon to tell the “Safe Removal” status at web page, but just turn off a USB LED to tell the USB disk is really unplugged from the USB port at this ‘unplug’ case. When a user press “REMOVE” button on the web page, then WebUI calls server side CGI “runtime” to handle the case of safe remove by calling core unplugging helper. The first step is to flush needed file system bufferes(caches) to USB storage for safety, the remaining steps are listed in the below flow chart. The later steps will also do “pre-unmount” the USB disk. When the user see the web page message box “You can safely remove the USB disk”, then he can really take the action of “remove” to the USB storage from USB port.