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Inconsistent write speed on USB flash drive

  • Flash Media
  • USB Flash
  • Storage
Last response: in Storage
July 30, 2012 11:43:31 PM

I've noticed lately that my USB transfers seemed to be taking longer from the front port in my computer. No idea how long it's been going on, really. I was kind of assuming my front ports were maybe USB 1.1 and the rears were 2.0, but was too lazy to check. (This is a new computer case)

Anyway, today I decided to see if the rear ports were any faster. I took a 16 GB TDK brand USB flash drive and popped it in the front-left port and transferred a single 160 GB file to the drive while timing it, then deleted it and rotated through the other five ports. Here is what I got:

front left....2m56s
front right ...0m44s
back bot left...0m24s
back bot right...0m23s
back top left...0m20s
back top right..0m20s

For giggles, I started to repeat the trials on a few ports and this time:

front left......0m13s
front right ...0m20s
back top left....2m55s

...So my slowest port in the first trial was front left 2 min 56 sec, but the second time it was only 13 seconds! The back top left was the fastest the first time at 20 seconds, but then was nearly 3 minutes the second time.

Running XP Home, SP3, several 1 TB HDDs, Intel P4 Prescott 3.00 GHz, 4 GB ram, D865PERL MB.

I have no idea where to go from here, but I'd like to get to the bottom of this. Any suggestions?

More about : inconsistent write speed usb flash drive

a b G Storage
July 31, 2012 12:00:31 AM

- I know it's a dumb question, but, you are transferring exactly the same data each time?

- The pc is in exactly the same state each time? - absolutely nothing going on in the background - you may want to repeat a few more times.

- that's quite a difference in the front left scores! - try repeating this a few more times.

- depending on the usb port used, a different hardware controller may be getting used (different hardware can easily yield different transfer rates) - again, more repeat testing required.

- data caching - more repeat testing required to normalise this.
July 31, 2012 12:14:32 AM

Yes, same exact file. I was just plugging it in, copying and timing, then deleting and moving it to another port. I think I might have had firefox or email open in the background, but I wasn't opening and closing applications.

I'm going to try again with another USB flash drive, but my computer is tied up analyzing some (actual work) data right now.
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a b G Storage
July 31, 2012 12:41:59 AM

It will be interesting to see the results with the other drive. I would also hit any one port with a minimum of 5-10 repetitions.
October 25, 2012 1:07:58 AM

My apologies for the long delay, but I believe I have solved the problem and wanted to update the thread in case anyone in the future was curious. It appears that the problem was in a setting in my BIOS on the D865PERL motherboard. Under USB 2.0 Legacy Support, I had "Full Speed" selected. I didn't consider that there might be a faster setting than "full speed", but apparently, there was. Setting it to "High Speed" fixed my problem.

Not sure how I missed it before, but:
HiSpeed = 480 Mbits/sec
FullSpeed = 12 Mbits/sec

I again transferred the same 165 MB file to two different 16 GB USB thumb drives and timed the transfer. I stopped testing after doing the three ports because of the obvious success of changing the setting.

USB PORT: Trial times for 167 MB file transfer (in seconds)
Front Left: 15, 12, 14
Front Right: 13, 14, 14
Rear Upper Left: 15, 14, 14

That is MUCH improved!