USB3.0 transfer (low) speeds??

martinlest · 21 Oct 2017

So many articles online on USB speeds of course, but I still can't work out why I have such low transfer speeds, or whether, under the circumstances, this is what I should expect in practice. Can anyone advise please?

I currently have two USB3 HDDs (1 x Toshiba 2TB & 1 x LaCie 5TB) connected to my PC and am copying files (lots and lots of files of mostly similar size - c.11MBs each. About 1.5TBs in total) from one to the other. My PC drives are two SSDs (Evo 850s 500GB each). The O/S is Win7 x64 (which I recall reading has issues in this kind of thing?). M/B = Asus H97I-PLUS

I use TeraCopy to transfer files, and the window shows around "2 MB/s" to 6MB/s". When I start up the speeds are faster, up to 40MB/s but soon slow down, which I am assuming is Win7? I do get bursts of higher speeds, c.25MB/s, sometimes up to c.45MB/s, but they don't last more than a few minutes.

I have checked Device Manager, which shows (Intel) USB3.0 enabled and the drives both show as 'Superfast' in USB Tree View (and similar) and as being connected to a USB3 port.

What speeds should I be seeing in the above circumstances? I read of USB3.0 capable (in theory) of ten times what I am seeing...

Thanks.

Megahertz07 · 21 Oct 2017

Believe me, I already done a lot of tests.
The bottle neck isn't the USB 3.x. The bottle neck is the disk.
The start up the speeds are faster because of the RAM buffer on the USB disk.
I have a External USB 3.0 case and only got high speeds with a SSD on it, and the results were the same with USB 2.0 Ports.

USB - Wikipedia
USB 2.0 = 480 Mb/s = 60 MB/s
USB 3.0 = 5000 Mb/s = 625 MB/s
USB 3.1 = 10000 Mb/s = 1250 MB/s

martinlest · 21 Oct 2017

Thanks... To be honest, I never understand the USB3.0 625MB/s given speed. What is that unit exactly? You surely can't move 1GB of data in under 2 seconds?? Is my average of about 4MB/s the best I am likely to get over a long transfer then?

the results were the same with USB 2.0 Ports

:) You know, I quite often move large transfers across to another PC which dual boots into Windows XP. Even though it only has USB2.0, I usually get much faster transfer speeds there than using USB3.0 in Windows 7. I may leave it running overnight on the XP PC to see if it finishes. On my main PC, the time left is still measured in days! (Has been at just 1MB/s for a few minutes - now it's transferring at 32MB/s, but the faster rate rarely lasts longer than a minute or so. I wonder why these jumps in transfer rate? Why would the buffer dictate that? The files being moved are all more or less exactly the same size and format, 11MB .dds files, after all).

LMiller7 · 21 Oct 2017

The USB3 bus transfer rate is in theory about 625 bytes/second. However, as with all serial protocols, there is some overhead so in practice the real maximum rate is about 500 MB/s. But that is just the interface between the drive and the computer and says nothing at all about the capabilities of the drive itself. Ads for USB drives usually don't mention that. Only a fast SSD can match that speed with conventional drives much less.

Megahertz07 · 22 Oct 2017

1 byte = 8bits
Computer transfer bytes. So the transfer speeds you see is MB/s not Mb/s.
But the advertising is always bits/s.
So USB speed is bits/s. Same for internet speed.
To move 1GB of data (8G bits) with a USB 2.0 will take (theoretically) about 20 sec, not 2 sec.

martinlest · 22 Oct 2017

Thanks Megahertz - I think I knew that at one stage, but had forgotten. If I move 1GB between my SSDs, it takes under 10 seconds; obviously HDD to HDD via USB will be a lot slower: I have to move/copy about 1.5TBs - about 2 days to do that I reckon!