Help me understand transfer rate for external USB 3.0 drive

By howardrg
Dec 10, 2010
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  1. I just installed a LaCie USB 3.0 PCI Express Card in my Vista 64-bit computer and plugged in a Seagate FreeAgent GoFlex Desk 2TB USB 3.0 external drive. The card literature says the transfer rate for USB 2.0 ranges up to 480Mb/s, and for USB 3.0 up to 5 Gb/s. If "Gb" means gigabits, the 5 Gb/s = 640 MB/s (five gigabits equals 640 megabytes). According to HD Tune, I am getting 106-113 MB/s on the Seagate. Is this a reasonable transfer rate for USB 3.0? I know that in the real world I'll never get 640 MB/s, but 106-113 seems a bit low. In any event, it tests faster than my SATA HD, which came in at 66-109 MB/s.
  2. SNGX1275

    SNGX1275 TS Forces Special Posts: 12,478   +292

    Looks fine to me. Your conversions are correct. The reason you aren't getting even close to the theoretical max speed is because the actual drive itself isn't capable of getting data out that fast. A good internal mechanical (spinning) HD at this time isn't going to be much if any faster than 120MB/sec. External drives are just internal drives put in an enclosure to allow it to be hooked up by USB, eSATA, or firewire (or any combination).
  3. howardrg

    howardrg Newcomer, in training Topic Starter Posts: 27

    Thanks for the reply. Good to know.


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