usb drive copy speeds vary a lot

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Level 1

6 points

usb drive copy speeds vary a lot

I have a Mac Pro and a MBP and often copy and paste files of 50 to 500 mb (image files or quicktime movie files mostly) using a usb flash memory sticks.

I have noticed that when I plug in the usb drives to any of the Macs and start to copy a file from it to the hard drive of the computers, the transfer speeds can vary greatly.

Sometimes when it starts to copy a file, the progress is very slow and I stop the process, then try again and the copy speed is very fast on the exact same file. Sometimes the file copy speed is very fast the first time I do it.
There is no discernible pattern or specific type of file that is faster or slower than others. It's just that the file copy/paste speeds are quite different in a random sort of way.

I notice that at work, where I have an older iMac not as powerful as my home Macs, the copy speeds there are generally much faster and more consistent.

Both computers at home have loads of memory and free disk space (Mac Pro 2.8 8-core 10 gb ram 4 large hard drives & MBP 4 gb ram 2,4 santa rosa processor, 80gb free on hard drive) and this happens with a variety of usb memory sticks. This has always happened so it's not a new development. I currently run osx 10.5.6 but it also happened on all osx versions I have had on the machines since 10.4.9.

Could I have some options set on my Macs that are affecting the copy/paste speeds or might it be caused by something else?
Thanks for any advice.

MBP 2.4ghz 4gb ram and Mac Pro 2.8 8 core 10 GB ram, Mac OS X (10.5.5)

Posted on Feb 19, 2009 4:25 PM

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Answer 1

Feb 19, 2009 4:56 PM in response to Luis Ortega

USB has 2 speeds, known as USB 1.1 and USB 2.0. USB 2 is fastest. You need to be sure of what type of port you are connecting to. Many keyboards support USB 1 only so you get slow transfers if you are connecting via them, some hubs have the same limitation.

Apple system profiler will tell you info about USB devices, Select Apple menu > About this Mac…, then click the More Info… button in the dialog. Select USB in the list, somewhere in that window will be all connected devices, find the disk and look at it's 'potential' speed value. In reality USB runs a lot slower than it's potential speeds.

480Mb/s is USB2 11Mb/s is USB1. The best way to get performance from USB drives is to connect directly to the Mac's USB ports. It could also help to remove all unused USB devices because USB is pants on the mac. Connect disks via Firewire if you want the best disk performance or Esata for breakneck speeds. Firewire is better with multiple devices and better at constant throughput.

Wikipedia has more info if you want to really get into it.

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Answer 2

Feb 19, 2009 6:15 PM in response to Luis Ortega

I use a USB hub and see this problem sometimes. I unplug, and plug into another port on the same hub and it works fine. I figure it's probably just detecting the media type incorrectly, possibly due to a non-compatible hub.

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Answer 3

Luis Ortega Author

Level 1

6 points

Feb 20, 2009 8:51 AM in response to Drew Reece (Re:co)

Thanks, I did check all that and the usb stick I use is usb 2. I always plug into the usb ports on the front panel of the Mac Pro, not the keyboard, and use the same ports on the MBP.
The problem is not the speed, but the fact that it is not consistent.
The same files, the same ports, the same usb sticks can react in wildly different ways.
One time it might start to transfer files very slowly and report an estimated time of 20+ minutes for a few large quicktime movie files and another time it might zip through the copying and only take a minute or two.
Is there any setting relating to how the computer caches stuff that might influence this operation?

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Answer 4

a brody

Level 10

85,314 points

Feb 20, 2009 9:21 AM in response to Luis Ortega

USB is often speeded up and down by processor speeds. That means if your processor is busy doing something while you are transfering files, it is likely to have to share bandwidth and slow down the USB bus. Double check of course that the item is connected to the high speed bus, and all items on that bus are high speed.

Furthermore, when copying to a flash drive that is FAT32 or FAT16 (the default for most of them), there are limitations to the amount of data that can be transferred at once, and that can slow down your transferred. If the flash drive is HFS+ formattted, you are less likely to see that problem.

If you must connect to a PC, it may be better to do an ethernet network to it, than using flash drives.

Verify also you haven't entered the realm of too little hard disk space free or room free on the removable media*:

http://www.macmaps.com/diskfull.html

Once that is entered, your file caching is slowed down.

- * Links to my pages may give me compensation.

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Answer 5

Feb 20, 2009 9:58 AM in response to Luis Ortega

I don't know of any caching that goes on with file transfers other than the built in bus speeds, these should be constant, but get shared with other tasks. USB disk speeds are also altered by other USB devices on the same bus so just have only one connected if possible.
Applications/Utilities/Disk utility should tell you the disk format as A Brody mentioned.

I'm afraid USB can just be flaky for no apparent reason. You'll find that smaller files will transfer at a different rate to larger ones, even if they have the same total size. Nested folders have another affect on speed. Testing would involve copying the same items onto each computer then transferring to the USB disk in question while running a stopwatch. The Finder guesses the transfer time based on how quickly it is copying the current file compared to the overall total. It doesn't take into account the numbers of files/ folders awaiting copy.

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Answer 6

a brody

Level 10

85,314 points

Feb 20, 2009 10:02 AM in response to a brody

Also, to verify items are on the high speed bus, go to the System Profiler's USB section and select the individual bus and make it drop down with its triangles to list the items. The System Profiler is in Apple menu -> About This Mac -> More Info.

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