FlyerTalk Forums - View Single Post - took Macbook Pro 10 hours to copy a 3TB drive to another 3TB drive, is that normal?
Old Feb 14, 2016, 3:05 am
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nkedel
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Originally Posted by weltfrieden
I bought another 3TB drive(same brand and model number) and hooked it up. I then selected all the files on the source drive and copied them to the new drive. It took a little over 10 hours for the copying to complete.
A 3.5" hard drive will typically have a limit of 100-125MB/second, or 8-10 seconds per gigabyte. 3TB = 3 trillion bytes as drive manufacturers use it, or abour 2793GB (or GiB) using the OS/RAM sense of 1GB = 2 to the 30th bytes rather than 10 to the 9th.

If you multiply that by 8-10 seconds per GB, that comes to between 6-8 hours. There's some overhead for USB, and there's some overhead if there are a lot of small files involved. So 10 hours is a bit slow, but not totally unreasonable.

USB 2.0 is limited to 480 Mbps, which in theory is 60MB/sec but in practice is more like 50-55MB/sec usable speed. At those speeds, the drive would have taken about 14 hours to copy, so you were getting at least some advantage out of USB 3.
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