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#1
Why does copying files start fast then slow down so dramatically?
I have a lot of files to move, about 1200GBs to go... The files are more or less all the same size, about 10MBs each. They are being copied from one external HDD to another, via USB3.0 and my Win7 x64 PC.
There are a number of external USB drives involved and they all do roughly the same thing. At first (could be several minutes or even an hour or more) the transfer rate shows as about 30MB/s, at which rate it would be complete in 3-4 hours. But after a while the rate starts to go down, fluctuating between fast and slow, until it can be as little as 1MB/s maximum speed, dipping lower (at which rate the transfer would take weeks).
I could understand if one drive was slow, it may have a fault, but all my USB drives do exactly the same thing. Why is it that a drive capable of moving files at 47MB/s (about the best I get) for some minutes slow down so much? It must be something in Windows 7? If I stop the transfer and reboot, it will set off again at 30-40MB/s.
There is always plenty of free RAM - never less than 12GBs free at the slowest copy speed. i7-4790K CPU @4GHz. Can't see anything obvious in Resource Monitor.. I don't do anything else on the PC whilst the transfer is taking place, as that usually slows down the speed within minutes- I just cut/copy and paste and leave it.
Tried with only system services loading (via ms config), but no change...
Any ideas? Thanks.
Last edited by martinlest; 11 Dec 2017 at 11:53.