我们都知道从我们的计算机上分离USB大容量存储设备有正确的方法和错误的方法，但是相同的原理适用于MTP设备吗？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

超级用户阅读器RockPaperLizard想知道你是否可以简单地拔下连接到Windows的MTP设备上的USB插头：

I know that after attaching a typical USB mass storage device to Windows, it is important to properly unmount the device before unplugging it in order to avoid the possibility of losing data. But for MTP devices (such as many Android devices) connected to a Windows computer via USB, is it necessary to perform any special or particular procedure before disconnecting the USB cable?

I am interested in understanding this for all versi*** of Windows (XP and later), so please include the applicable Windows version(s) in your answer.

你能简单地拔下连接到Windows的MTP设备上的USB插头吗？

答案

超级用户贡献者Carrein为我们提供了答案：

When plugging in USB mass storage devices, it gives a host computer undifferentiated access to the mass storage. It assumes absolute control over the file system similar to that of a hard drive.

As such, unless explicitly commanded by the host system to sever the connection between the devices, there is a chance that the host computer might corrupt the file system. Hence, the “Safely Remove Hardware and Eject Media” message.

However, MTP, or Media Transfer Protocol, operates at the file level rather than as a large unit of mass storage at the block level. When plugging in a device such as an MTP device, the host system queries the files on the device.

This is often maintained as a database or index in the root file system of the MTP device. The MTP device’s system does not have to rescan the entire device when its content is modified; it only needs to update the database/index.

The host system can then send a message to the device requesting that a file be downloaded, which will be sent by the device after acknowledging the signal. Deleting files works much the same way. The host system sends a message to the device, marking a file for deletion, then the device removes the file upon acknowledging the signal.

This works much like a transactional file system, where either the file is modified or it is not. The storage will not be affected by a failed transfer. This is also the reason why MTP only allows one file transfer at a time (atomic file transfer), so that corruption cannot occur as operati*** are run sequentially.

So yes, you can just pull the USB plug on your device.

Further Reading: Media Transfer Protocol [Wikipedia]

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图片来源：Jeremy Keith（Flickr）