Painfully slow data transfer to USB 3 devices on 2012 MacBook Air

Narial Taster

macrumors member
Original poster
May 17, 2011
35
2
I have a new 13" MacBook Air and found the data transfer speeds to external USB 3 devices to be underwhelming. I ran Blackmagic Disk Speed Test and the results speak for themselves. My 16GB USB 3 flash drive managed a paltry 16 MB/s write speed and a 66 MB/s read speed (Thumbnail attached.) A USB 3 1 TB WD Elements fared slightly better with both read and write speeds averaging at around 65 MB/s.

Could there be a hardware/ software problem with my computer or one of the drives? FYI, my internal drive has 400 MB/s read and 450 MB/s write speeds. Is this normal? And if not then can you guys think of a fix?
 

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kierennyc

macrumors regular
Dec 3, 2008
144
24
NYC
The bottle neck could be the actual devices you're transferring to.

Remember even though the external hard drive is USB 3, it can still only write or read as fast as the spinning platter allows. The same applies to memory sticks - they have their limits too.

The only way I believe to experience USB 3 at its best is to use SSD drives in a USB enclosure. But of course that isnt cheap or even necessary in most instances.
 

filmbuff

macrumors 6502a
Jan 5, 2011
809
142
I had a problem a transferring data when I first started using my Mac where speeds would start out fast (50-100 MBps) then grind to a halt and only transfer at 5-10MBps. The problem turned out to be something wrong with the permissions on drives partitioned by Windows (I had been using them on my Windows PC before). Erasing the drives and reformatting them in Disk Utility completely solved the problem.

I have a 500GB Momentus XT in a Rocketfish enclosure that gets ~90MBps and a Toshiba 1TB portable drive that gets 110MBps! USB 3 is fast when it's working.
 

Narial Taster

macrumors member
Original poster
May 17, 2011
35
2
Thank you all for your replies. I reformatted my flash drive as Mac OS Extended (Journaled) but the write/read speeds remain unchanged (16/65 MB/s). I was wondering if any of you have any experience with a USB 3 flash drive on the June 2012 Macs. If so then it would be great to compare the results.
 

carlos00

macrumors newbie
Jul 17, 2012
23
0
The problem is with the flash drive as max write speed are usually much lower than read or regular external HD's.
The Flash drive you have probably has an max write speed of 16MB/s - have you checked this against the specs of the flash drive?
 

Narial Taster

macrumors member
Original poster
May 17, 2011
35
2
You are right carlos00, the speeds that I am getting are in line with the specs of the flash drive. I was expecting a huge speed boost with USB 3. Thanks for clearing it up. However, I am curious as to why flash drives are slower than regular external hard drives. Shouldn't they be faster as they don't have moving parts?
 

SpoekGTi

macrumors regular
Jul 2, 2012
131
1
The Netherlands
I'm in the same boat with a brand new MacBook Air running Mountain Lion.

Image

This is frustrating to say the least.
This is not uncommon, cause your iPhoto library which tells you is 91 GB is in fact just a build up from all your photo's......which in your case would around the 26K photos consist which your drive (USB, TB, LAN or even fiber optic) cannot copy faster because it's just too many smaller files.

If you copy a real 91GB file you should be able to get higher throughputs
 
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KPOM

macrumors G5
Oct 23, 2010
14,505
3,050
You are right carlos00, the speeds that I am getting are in line with the specs of the flash drive. I was expecting a huge speed boost with USB 3. Thanks for clearing it up. However, I am curious as to why flash drives are slower than regular external hard drives. Shouldn't they be faster as they don't have moving parts?
Flash drives often use cheaper NAND to keep the price down. With some searching, you can find better drives with higher write speeds. Some of the better ones here have write speeds around 70MB/s, which is roughly on par with a platter hard drive.