Slow "Read" speeds on 2 new HDDs

Discussion in 'Mac Pro' started by CalfCanuck, Oct 18, 2012.

  1. CalfCanuck, Oct 18, 2012
    Last edited: Oct 18, 2012

    CalfCanuck macrumors 6502a

    Nov 17, 2003
    I just finished installing 2 new WD drives in my 2008 MP (bays 3 & 4). I ran the diglloyd DiskTester fill-volume test to condition them, and got some strange results - the "Read" results on both drives lagged write by a huge margin.

    Here's the 2 graphs, along with a sample from the Excel template (that matches early HDD tests from a few years ago).

    I turned off Spotlight and Time machine before the tests, and actually re-ran the 3TB drive test twice with everything running in my Dock turned off. Any ideas what is going on?

    1. WD Caviar Black, 2TB:

    2. WD Caviar Green, 3TB (for Time Machine).

    3. Sample graph, from excel template:

    (Edit: 10.6.8, 18GB)
  2. Spacedust macrumors 6502a

    May 24, 2009
    Seems to be ok. Mac Pro's doesn't have SATA/600 controller.
  3. CalfCanuck thread starter macrumors 6502a

    Nov 17, 2003
    Interesting. So if I had used a SATA II drive instead, I would have gotten better performance? I had assumed backwards compatibility, but not a speed hit...
  4. theSeb macrumors 604


    Aug 10, 2010
    Poole, England
    NO. There is no speed hit and SATA II is more than fast enough for a single HDD. I don't know exactly what type of files that test is using (small, large etc), but the results don't look like there is anything wrong. Everything looks perfectly fine.


    So what? A single HDD cannot saturate SATA II, so having SATA III will make no difference.
  5. derbothaus macrumors 601


    Jul 17, 2010
    You'd get the same performance on SATA1 actually. You need more than one HDD RAID'd to saturate SATA bus. (Some very fast exceptions) Like 1TB Raptor. SSD's are a whole other ballgame.

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