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I was in the middle of copying a lot of files on my Windows 8.1 system when suddenly the explorer process was terminated and restarted by itself. Afterwards I went to copy all the files again. Some were already copied, others were not copied at all, but I procceded to select all the folders and copied them again. Now in the end of the copying procedure Windows prompts me with a window "Replace or Skip Files?".

The explorer process resetted exactly because I was performing too many transfers simultaneously, that it reached a point where it throttled. I know this from experience as I've attempted the same thing in the past multiple times.

These are the files that were probably partially copied and now its asking me whether to overwrite them. Now since it is asking me this, then a file can probably be partially copied in Windows. But I want to be sure.

I also wander what happens If I moved instead, would the source file be partially "missing" as well? This is a question specifically about the Windows OS filesystem.

Thanks in advance.

  • If you are copying files on a fast LAN, Explorer should not terminate. If copying over a remote network, this can happen and in such circumstances, I only Copy - never Move lest I lose a file. – John Oct 3 '19 at 20:29
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Yes, a file can be partially copied if the copy operation is interrupted. Usually the partial copy will be smaller in size, but that's not guaranteed. It is much safer to re-copy the files.

For moves, the question is whether the move is done between different disks/partitions or inside the same one.

Moves within the same disk/partition do not involve copy but just a rename. They are next to impossible to interrupt and are never partial.

Moves between different disks/partitions can be interrupted, because at the beginning they just do a copy. When the copy is finished, the source file is deleted, but only after the target file was completely created. In that sense, such moves are safe enough - the source will not be deleted without the target being fully established.

The one interruption that can cause inconsistencies is power cut-off, since disk blocks that reside in memory are lost, blocks of both file data but also of folder meta-data.

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