slow USB 3.0 hard drive dock transfer speeds


#1

Slow transfer speeds with Plugable USB 3.0 Lay Flat Docking Station.

I just received the Plugable HD dock yesterday. I get really odd transfer behavior. This is on a Win7 machine, on the USB 3.0 port.

Initially, the transfer rate is fast (~100MB/s, mega bytes per second), at least according to the instaneous speed reported by the transfer dialog box in Windows 7. But transfer speed immediately slows down, and continues to slow down the longer the transfer goes. For a 5GB video file, the average speed is about 45MB/s from beginning to end. A couple times during the transfer, the system seems to pause transferring data. The progress bar stops, even though windows reports a high transfer speed. These pauses last 10 or 15 seconds, which is what really cuts down the average transfer rate.

I think there’s a memory buffer between the dock’s USB chipset and its SATA chip. In the beginning of the transfer, that buffer is empty, and the USB chip transfers at max speed to the buffer. The SATA chip moves the data from the buffer to the hard drive on the dock, but it can’t keep up. When the memory buffer fills up, the USB chip stops requesting more data, giving the HD dock time to catch up. Maybe the firmware monitors the buffer capacity and when it reaches critical, it stops and waits for the buffer to go below a threshold level before continuing the transfer. That would explain these 10 to 15 second pauses.

My system:
gigabyte ga-ma770t-ud3 mother board. The PCIe x1 slot seems to be PCIe 2.0, but I’m unsure. The x16 video slot is 2.0, but it doesn’t list the spec for the PCIe x1 slots. Even if it’s PCIe 1.0, the transfer rates should still be capable of over 200MB/s.

Pluggable USB 3.0 lay-flat Hard Drive dock (for SATA drives).
http://www.amazon.com/Plugable-Dr…B…

Syba USB 3.0 PCIe card (Etron chip)
http://www.newegg.com/Product/Pro…6….

By the way, I appreciate how you host issues on your forum. I like the transparency. Every company has issues with their product.


#2

Hi Eric-

Thanks for posting with such great details about the issue you’re seeing!

The first thing that springs to mind after reading through your post is that updating your Etron USB 3 host controller driver could help. Please verify which driver date and version your USB 3 Host controller reports in device manager, or send an email , attention Jeff, to support@plugable.com with the output from the DisplayLink support tool and I can check from this information. Please ignore any compatibility messages, as the tool was designed for another purpose- it’s just a quick way to get this relevant information. http://plugable.com/support/tools/dis…

I’ve also seen PCIe cards that weren’t seating properly due to bent/misaligned brackets yield inconsistent results.

Please let me know on the USB 3 host controller driver and we can move on to other steps if that isn’t helpful. Making sure to enable write caching for this drive may also help…

Sorry for a slow response, I should be able to reply more quickly going forward.

Best wishes-

Jeff Everett
MCITP Enterprise Support Technician
Plugable Technologies


#3

Jeff,
I waited until I got a new hard drive to test the dock again. As it turns out, my original hard drive might have been pretty fragmented.

On the new hard drive (5400 rpm WD green), I get about 90 MB/s (mega bytes per second) for large contiguous writes, and the weird pause during transfer went away until the very end. So I’m much happier with the dock performance. It’s probably pretty close to the write speed of the hard drive.

I wonder if the pauses I was seeing before was the hard drive seeking due to fragmentation on the original drive I tested on.

Thanks,
Eric


#4

Hi Eric-

Thanks for letting us know you’re seeing normal speeds from the dock on another disk.

To be honest there are far too many potential factors to speculate what was causing your slow speeds, however I’m glad to hear the dock is working well.

Please let us know if we can assist with other questions in the future.

Best wishes-

Jeff Everett
Plugable Technologies


#5