USB3.0 external drive 120Mb/s?

Discussion in 'iMac' started by imacken, Nov 19, 2015.

  1. imacken macrumors 65816

    Joined:
    Feb 28, 2010
    #1
    When I run BlackMagic Disk Speed Test on my Samsung D3 external USB3.0 drive, I get read and write speeds of 120Mb/s! My iMac late 2015 supports USB3.0, so why should that be?
     
  2. Jimios macrumors newbie

    Jimios

    Joined:
    Nov 7, 2015
    #2
    This is a pretty normal speed for a HDD, especially if it's 5400rpm. Your speed in this case is limited by the HDD rather than the interface.
     
  3. Samuelsan2001 macrumors 603

    Joined:
    Oct 24, 2013
    #3
    Because thats how fast HDD's are (well 5400rpm ones anyway the 7200rpm run to about 180Mb/s).
     
  4. imacken thread starter macrumors 65816

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    Feb 28, 2010
    #4
    Thanks for your help. Supposedly a 7200 in the Samsung, but.....
     
  5. tyche macrumors 6502

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    Jul 30, 2010
    #5
    115-120Mb/s is fast. That's already showing 7200 rpm disk speeds. That's why SSD and especially pcie versions are so awesome.
     
  6. m85476585 macrumors 65816

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    Feb 26, 2008
    #6
    The speed depends more on the density of data on the platters than on the spin speed. A 1TB 5400RPM disk will be much faster than something like a 160GB 7200RPM disk. Random seek might take slightly longer on the 5400 RPM drive.

    120MB/sec is fast for a spinning disk. A few years ago (maybe around 2010), people couldn't even comprehend that a disk could saturate USB 2.0 (around 35MB/sec) meanwhile my 1TB disks were showing 80-100MB/sec on eSATA. USB3.0 takes away a big bottleneck, but now the disk is the main limitation.
     
  7. jerwin, Nov 19, 2015
    Last edited: Nov 19, 2015

    jerwin macrumors 65816

    Joined:
    Jun 13, 2015
    #7
    That would be awesome for a USB 2.0 drive, which would be limited to 48 MB/s, so it's definitely USB 3.0.

    Still, Blackmagic shows my LaCie Minimus drive (7200 RPM) at 172 MB/190 MB, so perhaps the Samsung D3 isn't on the leading edge of spinning rust. However, this review

    http://www.techradar.com/us/reviews...hdd-ssd/samsung-d3-station-3tb-1183543/review

    says that 216MB/s and 203MB/s should be possible.

    So there's possibly some other things going on.

    Is it formatted as NTFS? HFS+? Is it encrypted?
     
  8. imacken thread starter macrumors 65816

    Joined:
    Feb 28, 2010
    #8
    Thanks for that. It's formatted as HFS+ and not encrypted.
    The review did say that those speeds were not seen in real-world tests', so, not sure.
     

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