underwhelmed by SATA III

Discussion in 'MacBook Pro' started by wildatheart, Nov 21, 2012.

  1. wildatheart macrumors member


    Nov 28, 2008
    I recently installed a SATAIII 750GB Momentus XT in the main bay of my 2011 17" MBP and I have a SATAII 500gb 7200rpm Hitachi drive in my optical bay. In system profiler my main drive is showing 6 Gigabit negotiated link speed, vs. 3 Gigabit for the optical bay drive, as expected.

    When I run Disk Speed Test, my main drive is showing speeds of around 75MB/s, whereas the supposedly slower connection in my optical bay is around 100MB/s. Is something amiss here?

    Many thanks for any thoughts
  2. leman macrumors G3

    Oct 14, 2008
    SATAII has maximal throughput of 300MB/s
    SATAIII has maximal throughput of 600MB/s

    Both are a way faster than any existing mechanical hard drives. What you are seeing is simply the Hitachi drive being faster. Where SATAIII shines are fast SSDs which actually can reach high speeds.
  3. wildatheart thread starter macrumors member


    Nov 28, 2008
    But, given that both are 7200rpm drives, should I not see a faster connection over Sata3 than Sata2, even if only marginally?
  4. leman macrumors G3

    Oct 14, 2008
    Well, there are slower and faster 7200rpm drives... I think that the individual performance characteristics are much more important here than a very marginal (at low transfer speeds) advantage of the SATAIII interface.

    Anyway, you should look for some Disk Speed Test benchmarks of that Seagate for comparison. It is possible that the drive is supposed to be faster.
  5. T5BRICK macrumors G3


    Aug 3, 2006
    I'm pretty sure most laptop HDDs don't have sustained speeds that would saturate a SATA I interface. If you want a faster drive, you'll need to look at SSDs.
  6. Ccrew macrumors 68020

    Feb 28, 2011
    Yup. While the link speed may be the same, the drive electronics aren't. There are fast drives, and there are slow drives. As you can see. There's a big difference between max speed and sustained speed usually


  7. naxir macrumors newbie

    Apr 15, 2012
    Also of note, I recall reading that momentus XT drives are slow at first while the SSD part is getting populated by files you use often. I'd run the test in a week or two and judge it then.
  8. wildatheart thread starter macrumors member


    Nov 28, 2008
    many thanks for the feedback - it just seems odd that an older Sata2 drive should be 30% faster than a new Sata3 drive.
  9. zeeklancer macrumors regular

    Jan 1, 2008
    The problem is the cable speed does not dictate the hard drive speed. The cable speed, SATAIII in this case is what sets the maximum speed the hard disk can transfer data at. That is if it can handle it.

    I should also point out that 7200 RPM vs 5400 RPM does not mean one will be able to transfer faster than the other. While we normally see higher transfer rates on 7200 RPM drives it really has little to do with it running at 7200 RPM. The RPM of the drive helps improve seek times. Lower seek times will help when you want to transfer many small files. But the RPM does not really play much in large file copy speeds.

    All that being said. Your hard disk are getting around what they should given that they are laptop hard drives. If you want faster you will need to invest in SSDs.
  10. NewishMacGuy macrumors 6502a


    Aug 2, 2007
    Couple things here:

    1. I have 2 Momentus XTs and they both test in the mid 90s MB/sec, which is in line with other tests I have seen posted here and on review sites. So your scores seem a bit off.

    2. It does take some use before you begin to see the real advantages provided by the NAND flash caching. I put one in my cMBP-15 on Friday and am just now getting to the expected 12-15 second boot times. Shutdowns still aren't as fast as they are on my wife's (which has been installed for about a month or so now). My frequently used apps all open instantaneously now.
  11. brentsg macrumors 68040

    Oct 15, 2008
    Any discussion of interface specs is just marketing speak with mechanical hard drives.
  12. wildatheart thread starter macrumors member


    Nov 28, 2008
    Many thanks for your thoughts everyone.

    What might cause mine to read at 75?

    It's ok to run Disk Speed Test from the drive that it is testing, right..?
  13. derbothaus macrumors 601


    Jul 17, 2010
    Bus width and drive speed are 2 different things. SATA has little to do with the speed of the drive unless you are saturating the bus. It is marketing and implied greatness that is the misunderstanding.
  14. leman macrumors G3

    Oct 14, 2008
    Running the benchmark from the system drive can definitely account for slower scores. The system will be doing other stuff with the drive as well, disrupting the benchmark.
  15. wildatheart thread starter macrumors member


    Nov 28, 2008
    Got it thanks - so if I install OSX on a partition in the optibay and test my main bay 'from there', I should get the true reading?
  16. leman macrumors G3

    Oct 14, 2008
    This would be definitively an interesting experiment :) If you do so - please let us know how it turned out!
  17. thedarkhorse macrumors 6502a

    Sep 13, 2007
    momentus xt won't show it's real benefits in a disk speed test. generally those tests sample a file of 1gb or larger, with the momentus xt the flash cache is for smaller files that you use a lot like OS files and apps. Large file transfers won't be any faster than a standard hard drive.
  18. wildatheart thread starter macrumors member


    Nov 28, 2008
    Will do (in a few weeks time)!

    Yes I imagined that might be the case - I only saw the XT result as surprising in relation to the older, other drive. It seems to suggest that the drive 'behind' the SSD in the XT is slower in certain circumstances than a good sata2 drive.
  19. b0fh666 macrumors 6502a


    Oct 12, 2012
    try CCCing your OS to the optibay drive and boot from there, then run the test on the main drive - should be an easy test.


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