I've got a USB 3 flash drive that should be able to write at about 50 MB/s, but I'm only able to write to it at 15 MB/s. I'm using a Mac Mini 2012, which has four USB 3 ports. I am connecting the flash drive directly to the Mac Mini, and not using a hub of any kind.

Are these normal speeds for the USB 3 ports on the Mac Mini 2012 when writing to a flash drive, or should they be much faster as I suspect they should? How can I get better write speeds to this drive?

The read speed for this drive is about 80 MB/s, so it's a bit more reasonable, although it should be 180 MB/s according to the specifications.

  • What does the drive specifications claim as the writing speed? Are you using big enough files to ensure that what you see is primarily the data transfer and not the file system navigation? Jul 10, 2013 at 22:36
  • It claims "up to 180 mb/s read" and "up to 50 mb/s write". I'm testing with 5 GB files.
    – Gary
    Jul 12, 2013 at 1:40

1 Answer 1


Depends on the speed of the flash. Most flash drives allow faster read then write since writing to a flash is a "destructive operation"

A site like http://usbspeed.nirsoft.net/ might provide further information.

As an example SSD drives are rates at a number of Input/Output Operations/s (IOPS) commonly read is faster then on even the best most expensive drives.

  • Yep I know it's the speed of the drive specifically. The reviewers for the exact model flash drive that I bought says that they got speeds of 150 mb/s write and 50 mb/s read. I'm not getting anything close to that. I'm wondering if the Mac Mini is known to have slower USB 3 speeds than say, a typical PC with USB 3 ports?
    – Gary
    Jul 10, 2013 at 21:16

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