SSD performance problem in ML

Discussion in 'OS X Mountain Lion (10.8)' started by Lucagfc, Jul 27, 2012.

  1. macrumors regular

    Joined:
    Sep 23, 2008
    #1
    Hi

    I' ve some problem with my Samsung 830 SSD after ML upgrade. When I installed the SSD 2 month ago the performance mesured with Blackmagic Disk Speed Test were: 380 MB/s write and 420 MB/s reading.

    Now I' ve 350 write and only 180 Mb/S reading! anyone have this issue? thanks!
     
  2. macrumors 68000

    steve-p

    Joined:
    Oct 14, 2008
    Location:
    Newbury, UK
    #2
    Is it still indexing Spotlight in the background, or maybe something else is running that's reading and writing a lot?
     
  3. macrumors 68000

    Reason077

    Joined:
    Aug 14, 2007
    #3
    Make sure you have TRIM enabled. You need to re-enable it after installing Mountain Lion.
     
  4. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #4
    Sppotlight is not indexing (no dot in the lenses in the top right cornet) and I' ve no other program running expect Mail, Safari and iTunes!

    ----------

    I' ve never enabled TRIM for my Samsung 830. After some web search I decided to not use that because it' s not necessary
     
  5. macrumors 68000

    Reason077

    Joined:
    Aug 14, 2007
    #5
    Sure, it's not necessary. But this is why you are seeing decreased performance over time.
     
  6. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #6
    I don't think that the disabled TRIM is the problem for me. disk has only 2 month and the benchmark with Blackmagic Disk Speed Test are really strange. The first test, now is good with 380 mb/s write and 430 mb/s read but after a couple of test the speed decrease to 200 mb/s and slowly increse at 300 but I don' t understand why! before ML installation after my last benchmark all works great.
     
  7. macrumors 68000

    Reason077

    Joined:
    Aug 14, 2007
    #7
    If you enable TRIM, you should get more consistent performance.
     
  8. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #8
    Ok, but before ML installation all works great and with the TRIM disabled. Why in ML i need to enable TRIM to have the same performance of Lion?
     
  9. macrumors regular

    Joined:
    Jul 9, 2012
    #9
    Check to see if your data is encrypted, if so, decrypt it.
    After installing ML, for some reason everything became encrypted slowing my Sammy SSD's down significantly.

    If you can, get Windows for bootcamp and update the firmware, that usually does the trick.

    As the others said, you should also try enabling TRIM.
     
  10. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #10
    Do you mean FileVault? I check that and it's disabled. For me install Windows is not simple. Is not possible to install bootcamp on external disk so I need to resize my Samsung 256 Gb and I prefer to not do that.

    I try to enable TRIM but the strange think is that the SSD performance change during the benchmark so in a really short time and It's a really strange thing!!
     
  11. macrumors 6502a

    jeremiah239

    Joined:
    Nov 1, 2007
    Location:
    239 Area, FL
    #11
    This guy really doesn't understand what TRIM is.
     
  12. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #12
    I kwow what TRIM is and I follow you advice and now TRIM in enabled but nothing changed. The performance drop after 2 or 3 read/write test are still there.
     
  13. macrumors 68000

    Reason077

    Joined:
    Aug 14, 2007
    #13
    There's no difference between SSD performance in Lion vs. Mountain Lion.

    What you are probably seeing is reduced performance over time due to not using TRIM, and this might be particularly noticeable after installing a new OS, because OS installation means a huge number of files are getting deleted and new files being written.

    See this article for a good explanation of how TRIM improves performance:

    http://en.wikipedia.org/wiki/TRIM

    Basically it comes down to this: Flash NAND cells must be erased before they can be written to, which takes time. Normally an SSD has no way to distinguish between blocks that contain live files and those which contain data that has already been deleted, so it can't erase the unused blocks straight away when you delete a file. That means when the OS writes a file to a block that has previously been used, the write will be slower.

    What TRIM does is gives the OS a way to say "hey, this block has been deleted, you can go ahead and really erase it now".

    While SSDs do contain mechanisms that work around the lack of TRIM somewhat (eg: garbage collection), it's better to enable TRIM if you can.

    ----------

    You need to give it some time. TRIM may not have an immediate effect, but it should improve performance over time as files get deleted and unused blocks are TRIMed by the OS.
     
  14. macrumors 6502a

    jeremiah239

    Joined:
    Nov 1, 2007
    Location:
    239 Area, FL
    #14
    This
     
  15. macrumors regular

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    Oct 23, 2011
  16. thread starter macrumors regular

    Joined:
    Sep 23, 2008
    #16
    I really appreciate you post but I already knew the theory behind the TRIM.

    My question is: The flash cell need to be erased before new write operation so the TRIM in theory should only influence write performance. But I have problems in reading performance. This in the really strange thing!
     
  17. macrumors 68000

    Reason077

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    Aug 14, 2007
    #17
  18. macrumors regular

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    Oct 23, 2011
    #18
    I had read in the past that this program replaces a system file instead of patching causing more trouble than good. Have they changed they way it enables trim?
     
  19. macrumors 68000

    Reason077

    Joined:
    Aug 14, 2007
    #19
    Recent versions of Trim Enabler work by patching and thus are fine with all the various different OS X versions, including Mountain Lion.
     

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