I was copying the windows "users" folder for a friend of mine and I noticed that the 6.5GB file took unusually long to copy. The transfer rate never exceeded 5Mb/s. Also, I noticed there was an unusually large amount of folders: 30,000-40,000. Does a high number of files, folders and subfolders have a bad effect on transfer speed?

The transfer mentioned was done between an SSD and a USB 3.0 flash drive.

  • USB 2.0 or USB 3.0? It is normally for a user's profile directory to contain a good amount of files.
    – Ramhound
    Aug 25, 2015 at 22:25

2 Answers 2


When you copy data, the ideal case is having one sequential file. Instead, having a myriad of small files kills performance. A mechanical disk has to keep seeking for the right sector, and this is very time-consuming; an SSD is much faster, but still it suffers. If you check an SSD benchmark (I recommend Anandtech) you'll see that sequential read is often around 500 MB/s (assuming a SATA 3 connection, which is the most common), whereas reading chunks of 4KB is much slower, less than 100 MB/s.

Moreover, you are copying from an SSD to a USB drive. The latter is probably your bottleneck: consider that a USB 3.0 interface doesn't guarantee that the device will operate at that speed, but rather that it could transfer data up to that speed. Many cheap USB drives have a low quality memory and/or controller, and they are slow, so slow that USB 3.0 is actually useless as they couldn't even saturate USB 2.0.

In your case you are probably seeing a combination of the 2 things, the many files and the slow USB drive. The result is that the operation takes longer than other file copies.


the amount of files causes both the usb and computer to search for each file and have to restard the transfer process for every file. you will transfer huge amounts files faster by compressing them all into one file using a copressing program such as winrar, then decompressing the files once they are on the other computer.

transfering say 40 thousand files can take an hour as the process is stuck on 4-6 mb/s as each file has to be looked up, copied, located its location to be transferred then pasted, then possibly deleted if ur not coying. then checked.

if u compress all the files into one compressed file it will just transfer it all at once without having to do the look up or searches as all the location of the files are stored inside the compressed file. this will only take 5-10 minutes to compress, 5-10 minutes to transfer to the usb then onto the other computer, then a couple of minutes do decompress. will end up at about 20-30 minutes which is still faster than the 1 hour it would take to just copy all the files onto an usb.

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