我们都听到过这样的警告：当我们使用完USB设备后，要安全地将其卸下，但如果操作系统被挂起，而您决定只需在当时或那里拔下USB设备，那该怎么办？今天的超级用户问答帖子回答了一位好奇的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

问题

超级用户读者IQAndreas想知道在计算机挂起时删除USB媒体是否安全：

We are often cautioned against unplugging USB drives in case they are currently being read from or written to. When a computer is suspended, hibernated, or asleep, it is obviously not writing any data. It may have been in the middle of a read or write operation, however, and it will have put such an operation on hold.

Since no arms are moving (for USB hard drives), or bytes on the drive flickering on and off (for flash drives), is it then “safe” to unplug the drive in question?

Is this true even if data was being written to it, but the operation was temporarily suspended? (Assuming you do not mind that specific file having been only half-written to the USB drive.)

当计算机挂起时删除USB介质安全吗？

答案

超级用户贡献者kinokijuf为我们提供了答案：

While there are indeed no transfers going on, the reason you do the Safely Remove Hardware dance is not because of the transfers. You are doing this to cleanly unmount the file system. Programs may still be using the USB drive and some files may still be unwritten to the disk, even after the application using them is closed. This is the same reason why you do not just hibernate and switch operating systems. A mounted file system is never guaranteed to be in a c***istent state.

Ever wondered why an operating system slowed down to a crawl when using floppies? It is because the cache was flushed after writing each sector so that the floppy could be removed at any time when not in use.

You will still get a dialog pop-up and your program will hang if you try to access a floppy that was removed behind your back. Just insert the floppy back and be done. This will not work with USB drives because they get a different identifier each time. The program will just crash and the operating system may too if a driver was accessing a file.

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