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I was moving a file about 180 Megabytes from my external hard drive (7500 rpm, 1 TB) to my 8GB flash drive. It was moving at about 20-40 Megabytes per second when the speed started to drop down to 2 Kilobytes per second until the file transfer was complete. Is this normal? (Windows 8.1, i5, 12GB ddr3 ram)

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  • What is the brand/model of your hard drives?
    – Ben N
    Nov 22, 2015 at 17:38

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A slowdown is very normal. Informartion is NOT copied from the external harddrive to the USB pendrive. Instead it is read from the harddrive to a buffers in memory, and then that buffer is written to the pendrive.

How these buffers are used depends, but typical it will start with max read speed until a certain amount of buffers are filled, and then slow down to write speed.

Now the initial 20-40MB/sec sounds just about right for reads from an external USB drive. 2KB/sec writes on the otherhand are very slow.

To find out what is wrong to these two things first:

  1. Read from the external drive to your internal drive (e.g. to D:).
    That should be limited by the slowest I/O, which is likely from the external drive. So expect the same 20-40MB/sec. This will exclude the reading part from the list of problem sources.
  2. Write from internal disk to the USB pen drive. How fast is this? If it is 2KB/sec or faster (writing to pen drives can vary from 2MB/sec to about 25MB/sec, depending on the model. If it is 2KB/sec then pleae post what you are copying. E.g. for thousands of small text or c files to a pend drive with standard windows settings is normal. This is due to the way the safe removal settings are configured in windows.

If neither is slow then you different USB ports and check cables.

Regardless, some more information in the original post is rather welcomed because right now all we can do is semi guess...

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