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I guess I'm trying to pinpoint what chokes the transfer speeds in general:

Situation is - Brand new Dell E7240 with USB3.0 ports. Copying from a USB3.0 capable card reader (Lexar).

Lots of individual files. Crystalmark says my IO on the [SSD] drive for 1GB files is ~350MB/s at the SLOWEST test (450MB/s at the highest).

Copying actual files, maxes out at ~48MB/s. the files are all between 8MB and 50MB a file, and there's 26GB in total on the SD card.

I've tried using unstoppable copier and changing the copy policy on the reader to "faster" and both only increase copy speeds (each by themselves) to around 54MB/s tops.

My question is this: What factors are the greatest in preventing the copy speeds from reaching the theoretical maximums? - Multiple files? - USB Card quality? - Copy method? (i.e. instead of files, just an image of the SD card would be faster as it's one continuous stream of data).

Any other thoughts / ideas?

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  • Are these regular SD cards or high speed SD cards?
    – fixer1234
    Commented Nov 10, 2014 at 5:21
  • On this post: superuser.com/questions/834885/memory-cards-for-tablets, a high speed card (300X) was listed at 45 Mb/s.
    – fixer1234
    Commented Nov 10, 2014 at 5:27
  • These cards are 1000x. Site says 160MB/s. Could be a faulty card or card reader - he's going to get another brand of both.
    – Dave
    Commented Nov 10, 2014 at 8:30

3 Answers 3

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Problem could be "all of the above", with the more likely candidates being a low quality USB card or (a distant second) possibly a bad USB driver. Does the SD Card have a number on it ?

The multiple files are unlikely to be the issue if coming from SSD.

It could also be a faulty cable, faulty reader. But the SD card speed is the most likely candidate - SD cards are, as a rule, not that fast (but there are exceptions).

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  • Cheers Davidgo. We'll look at the SD card as the culprit as he did mention they weren't high quality.
    – Dave
    Commented Nov 10, 2014 at 6:17
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I had this issue also. 95mbps cards and getting 250kbps transfer times. Turns out the cable was at fault. Tried a new cable - all good.

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I agree w/ davidgo. There are some new sd cards out that have transfer rates up to 225 Mb/s now. If you are using anything under 95Mb/s, your transfer speeds will be atrocious. If it's a high quality card, transfer speed [Maximum] will be stamped right on it, otherwise expect it to be slow. I use an sd card for my environment variables [tmp Temp virtual memory browser cache etc] in Win XP with tremendous results for speed. But, the card must be fast enough to make it worth the cost. Sandisk [Pro series] makes the fast high quality ones - search Ebay or Amazon.

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  • To express your agreement with other answers, please just upvote them. Aside from that, your answer doesn't seem to contain any new information that answers the question.
    – David Richerby
    Commented May 20, 2015 at 7:39

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