I have two 500 Gb hard drives. One is USB 2.0, the other is USB 3.0. My intention is to use one of these hard drives for Time Machine, and the other for storing media files on (mp3s, mp4s mostly).

Would it be a waste of the USB 3.0 speeds to put Time Machine on that drive, or will I benefit.

  • What computer do you use?
    – bot47
    Jan 18, 2013 at 10:48

3 Answers 3


It depends. I assume your Mac does has USB 3.0 support since you asked the question.

Time Machine target does not need to be very fast, since Time Machine only backup all your files for the first time, it's just delta (changes) it backups after that. So if you delete a file, and create a new file, it backup just those two changes.

But of course the faster the drive, the faster the initial backup.

Media drive don't have to be fast. Even a 1080p video won't exceed like 2MBps, and most USB 2.0 drive can easily go up to 20 ~ 30 MBps (real world)

It's your choice. Again, you need to copy all the files to your external drive, and it takes time.

If they're enclosure, then problem solved. The initial backup and media copy can all be done with the USB 3.0 enclosure, and then just choose which goes to which based on your mood.

My personal experience:

USB 2.0 3.5" 28 MBps

USB 3.0 2.5" 55 MBps

USB 3.0 3.5" 110 MBps

All enclosures, I built them myself!

  • I would add that increased speed in Time Machine wouldn't be a bad thing - you could have delta updates still take up quite a bit of space, and take time. The faster the drive, the faster the computer runs Time Machine, and gets back to normal - versus HD video which won't saturate the USB2 pipe.
    – jmlumpkin
    Jan 20, 2013 at 21:04
  • A very useful answer. We covered some of these general concepts over here but it's very nice to have USB 3.0 experience documented. Have you found the drive to be a limiting factor ever in your builds? I wonder what the 2.5 inch drive at 55 MBps would push on USB 2.0.
    – bmike
    Jan 22, 2013 at 22:13

The only time you will be waiting for Time Machine is when you restore a huge amount of data in case of an accidental erasure or a full system restore.

Unless you have other resource issues or problems, Time Machine should be a background process and never slow the operation, so most people put their slowest drive on backup duty. Furthermore, the nature of Time Machine where only changed files get written, you have huge data compression and a fraction of the data gets written each incremental backup.

Unless your other use of the drive is even lower priority than the initial backup, the eventual restore - you would want to keep the faster drive for things you need to wait for a copy or a use and let the system wait for the slower drive when it's running normal backups in the background.


If you have fast HDs (Eg, Wester Digital Caviar Black doing 155MB/s 1 , or almost any SSD) then you may be limited by the USB 2.0 rates.

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