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I have a Corsair Voyager 32GB DiskOnKey, and when I transfer files to it, they're written very fast, but the move operation halts after each file. Write, halt, write, halt for each file written. I was wondering what could cause it? Usually it's done by AntiVirus software, but I also have an external HDD in which this doesn't happen. All of the basic Vista protections are off. The only thing I've changed in the device itself is reformat it with NTFS with a block size of 512 bytes. But I haven't ran the device with any other file system, so I don't know if this is the problem.

I also tried to work with it on XP on another computer, and it happens there too.

Though I haven't measured the halt after each file transfer, it seems correlated to the file size. Small files have clearly shorter halts than large files.

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This may be related to write caching. I think the default setting pre-XP was for flash devices to have write-caching enabled, which makes the write operation appear to finish quickly, but in reality it's cached quickly and the actual writing takes place in the background. This was why you could easily have file corruption if you copied a large amount of data to the flash drive and removed it (without stopping the device using the safe removal dialog) before the background writing had completed.

This was changed in XP, write caching is disabled by default, so that what you see in the user interface (e.g. file copy dialog) matches what is actually happening, i.e. when the copy dialog is done, so is the writing. This also means less chance of file(system) corruption, unless you happen to unplug the drive while a copy operation is still in progress.

You can check this in device manager, expand "Disk drives" and double-click the device that corresponds to your flash drive. Take a look at the "Policies" tab and I'm pretty sure you'll see that it is set to "Optimize for quick removal".

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Please correct if I'm wrong, but I believe this is related to a move in Windows being a Copy-then-Delete method.

So, it's copying the file, then deleting the old, then going to the next one.

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It happens both in cases that the file copied is deleted and when it is not deleted. But nice shot. –  Avihu Turzion Aug 31 '09 at 8:43

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