I got a brand new 3TB Seagate FreeAgent external disk. But it is TERRIBLY slow! Slow as a dead rabbit. Is it because of the USB 2 connection it uses? (Unfortunately is has no SATA connector). It sucks.

I used Disk Tools to measure the speed. Look how fast are my old drives compared to the brand new one!

Drive D: - [freeagent 3tb] --------- THE NEW ONE Free space: 2376.10GB OS buffer: disabled

      Write speed: 20.4MB/sec
      Read speed: 25.22MB/sec

Drive E: - [Old] Free space: 69.88GB OS buffer: disabled

      Write speed: 67.5MB/sec
      Read speed: 65.60MB/sec

Drive C: - [toshiba-500gb] Free space: 146.45GB OS buffer: disabled

      Write speed: 75.0MB/sec
      Read speed: 81.29MB/sec

Is this normal?

  • As I searched for the benchmarks of this model and yes they are showing that this is slow HDD. You can also see my this answer. – avirk Jun 7 '12 at 14:34

Quoting from the Wikipedia USB article:

According to routine testing performed by CNet, write operations to typical Hi-Speed hard drives can sustain rates of 25–30 MB/s, while read operations are at 30–42 MB/s; this is 70% of the total available bus bandwidth. For USB 3.0, typical write speed is 70–90 MB/s, while read speed is 90–110 MB/s.

So it indeed sounds like the USB 2 connection is the bottleneck.


USB 2.0: Released in April 2000. Added higher maximum bandwidth of 480 Mbit/s (60 MB/s)

USB (2.0) on wikipedia

Remeber, this is the upper limit. There is a great chance that the protocol to communicate with the USB device controller slows the communication down or that the firmware on the controller is implemented cheaply.

This is probably not caused by USB 2.0 alone, but by the casing you put the drive into.

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