USB 3.0 HDD Transfer Rates


Staff member
Dec 14, 2002
New Jersey
I have been moving files around, archiving stuff, and found what I thought was an interesting set of results.


I moved 1.84 TB of files from an old 2TB USB 3.0 drive to a new 5TB USB 3.0 drive, over two USB 3.0 ports on my MBP.

Per Carbon Copy Cloner, this happened over 7h38s. My calculations make that around 66MB/s. See "Backup Task"

Verifying the checksums of the files ("Backup Task 1") took about the same time.

I keep my iphone backup on an external SSD (Samsung T5). I have it coded on my mac to find that drive and backup to it.

I wanted to move the iphone backups to this new drive, just as a spare copy. So I moved 246GB of backups to the 5TB drive.

My calculations (see "Backup Task 2") show that this transferred at around 97MB/s.

The checksum verification for this (iphone backups are really hundreds of thousands of little files it seems), is "Backup Task 3". Interestingly, doing the checksum on all these files, on the faster SSD drive, took longer. I assume that means the bottleneck is reading of the copy from the drive I wrote to, since it is a spinning 5TB HDD.

Im actually surprised that I got between 66-97 MB/s write speed on an external USB 3 HDD. It seems like some optimized sequential write benchmarks are in the 100-120MB/s for files written from a computer to a HDD, in a benchmarking SW suite. But this was from an old HDD to another HDD, both USB, and from a USB SSD to a USB HDD...


Im looking forward to using thunderbolt and USB C to a greater capacity going forward, but Im reasonably happy with these results. Seems faster than Id expect...
Oct 30, 2002
Great Lakes
66MB/s sustained rate over USB is very good, you should be most pleased.
Agreed. That's roughly what I get when copying data between two external HDDs (non SSD) over USB 3.0. That's with medium to large files. If you're copying lots of small files, your transfer speeds will suffer quite a bit.