Samsung Evo 750 unexplained low random reads

Discussion in 'MacBook Pro' started by whitedragon101, Nov 19, 2013.

  1. whitedragon101, Nov 19, 2013
    Last edited: Nov 19, 2013

    whitedragon101 macrumors 65816

    Sep 11, 2008
    My System
    Early 2011 MBP 17" i7 8gb RAM , 7200 Hitachi HD 500GB -> Samsung 750 Evo
    I have just put a Samsung Evo 750 in my Macbook pro. To do this i used Carbon Copy Cloner from my HD I then put in a bootcamp partition and installed windows7 manually.
    I have a 638GB OSX partition and it has 358GB free.

    The problem
    I now decided to benchmark the Evo in OSX using xbench and the Random 4k read number is 24MB/s .That is nearly half the number it is getting in reviews. (the reviews are in windows not using xbench)


    1) Any idea why this would be (low 4k random read speed) and how to fix it?

    2) Does anyone else have a Samsung Evo? or even another current gen ssd? If so could you bechmark in xbench (its free and takes seconds to do) and let me know what you get?

    Results 628.58
    System Info
    Xbench Version 1.3
    System Version 10.9 (13A603)
    Physical RAM 8192 MB
    Model MacBookPro8,3
    Drive Type Samsung SSD 840 EVO 750GB
    Disk Test 628.58
    Sequential 379.15
    Uncached Write 860.49 528.33 MB/sec [4K blocks]
    Uncached Write 573.54 324.51 MB/sec [256K blocks]
    Uncached Read 158.06 46.26 MB/sec [4K blocks]
    Uncached Read 759.03 381.48 MB/sec [256K blocks]
    Random 1837.21
    Uncached Write 2130.81 225.57 MB/sec [4K blocks]
    Uncached Write 1119.46 358.38 MB/sec [256K blocks]
    Uncached Read 3468.25 24.58 MB/sec [4K blocks]
    Uncached Read 1900.09 352.57 MB/sec [256K blocks]

    3) If anyone has any other mac ssd benchmarking software like quickbench please let me know what you get on your drive
  2. costica1234 macrumors member

    May 21, 2013
    I have the exact same model of SSD, but installed on a 15 inch non-retina mid-2012 MBP, 2.6 i7 & 8GB RAM. I get similar results to yours:

    Attached Files:

  3. johnnnw macrumors 65816


    Feb 7, 2013
    My results with a 9 month old 256GB Samsung 840 Pro

  4. Macman45 macrumors G5


    Jul 29, 2011
    Somewhere Back In The Long Ago
    The speed you are going to get is dependent on the SATA bus speed of your Mac. The SSD may well be capable of speeds far in excess of what the older SATAII can support.
  5. devilcm3 macrumors 6502a

    Jan 3, 2011
    South Melbourne, Australia
    the 2011 MBP should have SATA III.
  6. whitedragon101 thread starter macrumors 65816

    Sep 11, 2008

    Thanks guys. It must be the way the benchmark works rather than a fault with the drive.
  7. ls1dreams macrumors 6502

    Aug 13, 2009
    I freaked out when I ran xbench just now, but my numbers look similar to yours. I'm guessing it has to do with how xbench calculates it / runs the test.

    Also, on 2011 macbooks, the primary SATA channel is SATA6, but the optical bay is only SATA3. Future models were both SATA6.

    Results 513.70
    System Info
    Xbench Version 1.3
    System Version 10.9.1 (13B42)
    Physical RAM 8192 MB
    Model MacBookPro8,1
    Drive Type Samsung SSD 840 EVO 250GB
    Disk Test 513.70
    Sequential 307.07
    Uncached Write 816.32 501.21 MB/sec [4K blocks]
    Uncached Write 534.76 302.56 MB/sec [256K blocks]
    Uncached Read 117.50 34.39 MB/sec [4K blocks]
    Uncached Read 703.90 353.78 MB/sec [256K blocks]
    Random 1570.49
    Uncached Write 1648.40 174.50 MB/sec [4K blocks]
    Uncached Write 962.71 308.20 MB/sec [256K blocks]
    Uncached Read 3123.24 22.13 MB/sec [4K blocks]
    Uncached Read 1719.97 319.15 MB/sec [256K blocks]
  8. paul-n macrumors regular

    Jul 12, 2012
    The 4K read speeds are always low, which is the reason why it usually makes no felt difference between using SATA 3 Gb/s or 6 Gb/s.
    If you compare the data with HDD you have values below 1 MB/s. This is the reason why SSDs help to increase performance.

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