Transfer rates between HDs not the same both ways

aalwees

Commendable
Jul 19, 2016
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I'm puzzled by the fact that the transfer rates between my two WD 1Tb hard drives is so vastly different - nearly half the one way compared to the other.

The one drive is a removable backup on a USB3 port and benchmarks at over 120Mb/s, the other is a WD Blue, an internal drive, which benchmarks at about 180Mb/s. When I transfer from the external to the internal I get nearly 120Mb/s but when I transfer from the internal to the external I only get about half that, with the result that backups take much longer than they should.

But the really strange thing to me is that this was not the case when the external was FAT32. I reformatted it NTFS because FAT32 gave me hassles with big files.

Does anyone have any insight on this? Should I go back to FAT32 for the external?
(I'm on Win7)
 
Welcome to the community, @aalwees!

These transfer rate benchmark results seem to be accurate for both the external WD drive and the internal WD Blue. Keep in mind that the USB 3.0 connection is slower than the SATA one, so I'd say the speed differences are normal. How do you do backups onto the external drive? Do you use any specific software or are you backing up the files individually?
The copy/paste backups of larger files onto the external could also be influencing the transfer rate performance, but at least you don't have the same file size limitations as those in FAT32. I'd not go back to it, unless you are using a device with the WD External HDD that is not reading NTFS.

Instead, I'd recommend you try using externally-powered USB hub. Hopefully, it would improve the write speeds.

Keep me posted!
SuperSoph_WD
 

aalwees

Commendable
Jul 19, 2016
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Thanks for your response SuperSoph_WD and zerooneoneoneoneoneoneone ;-)

I'm struggling to see how the usual disparity between read and write speeds on a drive might be relevant here. I'm talking about a massive disparity in write speeds between an external and an internal in a situation where the capacity is there for 100Mbs+. I can think of no reason why I shouldn't get similar write speeds going both ways.

Besides, this goes way beyond the usual disparity between read and write speeds. When I do benchmark tests on the drives I get a disparity of 5 to 20% (lower with the big files). I figure, there'd be a far bigger disparity when reading from one part of a drive and writing to another because the drive must read and write at the same time but I'm talking about reading from one drive and writing to another very similar drive in a setup where the capacity provides for over 100Mbs either way. Yet when I write to the external I get half the speed, sometimes less than a third, than I get when I write to the internal. It's the write speed disparity, not the read-write disparity that puzzles me.
> External to internal: 100 to 120Mbs+.
> Internal to external: about 50Mbs, sometimes less.
(The copying kicks off at full speed and quickly tapers off to about half. When I do an ATTO benchmark on the external, I get write speeds of at least 100Mbs.)

In this instance it's a matter of drag-and-drop copying large folders from the one drive to the other. I do this is without using the system in any other way at the same time.

The external drive is externally powered. The USB3 port provides for a real world speed of around 100Mbs both ways.
The internal is a WD10EZEX-00WN4A0 1000.2 GB
The external is a WD10EZEX-21M2NA0 1000.2 GB

Thanks for applying your mind to this SuperSoph_WD. I gather you're a WD rep. I've had Seagates for the past 8 years and didn't notice the problem then, but maybe it's just because my new Western Digitals are overall so much faster that I notice this! :)
 

aalwees

Commendable
Jul 19, 2016
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Here's another piece of the puzzle:
I did some tests copying between my internal SSD and the Western Digitals and got a perfectly normal consistent and high write speed to the internal: 170Mbs+ but again, much lower to the external: around 70Mbps.
1. Why would the write speed to the external be faster from the SSD than from the internal HD?
2. Why is it still so much slower than the drive's ATTO write speed of over 100Mbps?
I was expecting real world rates of about 100 from my setup, not 70 and certainly not 50.

Could this be something to do with the external's housing? It's a Coltech.
 
Hey there again, @aalwees!

It is definitely puzzling! I'd recommend you manually reinstall the USB Hub controller drivers from the motherboard manufacturer's official website and make sure you have the latest ones installed from there, if you haven't done this already. It could also be the external case that you are using, so I'd recommend you try with a different one, if you have a spare somewhere around, or a docking station.
You mentioned that the external is formatted in NTFS, but what is the allocation size you used? I'd also suggest you check your USB Legacy mode in BIOS. I'd suggest booting into BIOS and checking the 'Advanced' or 'Drive' settings, if you have Legacy USB Support enabled, make sure you disable it.
Another thing you should check is the Policies tab in Device Manager > Disk Drives > the external HDD. You should see two removal policies there. I'd recommend you check 'Better Performance' and enable 'Writing disk cache'. Have you tried defragmentation of the disks and tracking the performance while plugged to a different USB port on your computer?

1. Why would the write speed to the external be faster from the SSD than from the internal HD?
The solid-state drive is a lot faster than any other mechanical hard drive, this would explain why the write speed from it to the external HDD is slightly faster.

2. Why is it still so much slower than the drive's ATTO write speed of over 100Mbps?
The SATA-to-USB environment takes out quite a bit of performance when any mechanical HDD is put in such an external enclosure. The theoretical speeds (those listed in the benchmark software apps) can rarely be reached. External hard drives rarely hit 120MB/s both write and read over USB 3.0. As I already mentioned, the amount and the size of the files that are being transferred could also influence these stats.

Hope this was helpful. Let me know how the troubleshooting is going, though. :)
SuperSoph_WD
 

aalwees

Commendable
Jul 19, 2016
4
0
1,510
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Thank you so much, SuperSoph_WD. I'm going to dig into the BIOS and drivers tonight.

Re 1 and 2, the lowest common denominator, as far as I can see, is the USB port and it allows for a proven working capacity of around 100Mbs to a drive that I know has a write speed capacity in that range for the sort of file sizes I'm moving. I know the USB3 speed because I get it on the up and for a short burst initially on the down. I know the real drive write speed because it's practically the same as the internal one which does achieve that. So the additional speeds of the SSD and SATA are irrelevant and the drive write speed is not the lowest common denominator. What I need to figure out is why I'm not consistently achieving write speeds on par with the lowest common denominator.
 

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