Ssd wear in Fusion Drive?

Discussion in 'macOS' started by toke lahti, Dec 2, 2016.

  1. toke lahti, Dec 2, 2016
    Last edited: Dec 3, 2016

    toke lahti macrumors 68000

    Joined:
    Apr 23, 2007
    Location:
    Helsinki, Finland
    #1
    I just read this:
    http://arstechnica.com/apple/2016/0...-good-and-bad-in-apples-new-apfs-file-system/
    After my ssd died from my mp3,1's fusiondrive, I've been thinking how to prolong next ssd's and system's life.
    In the article it was said that there's no help ftom Trim command to ssd, when ssd doesn't have enough free space.

    Is ssd always full in fusiondrive?
    Would it be helpful to make a bit smaller (than the whole storage space in ssd) volume to ssd, which is then used in fusiondrive?

    Is there a difference how Trim works in 10.10 & 10.11?

    EDIT: By "full" I don't mean 100% full to the last bit, so you can't write anything to it, BUT something like 90% or 95% full, meaning that Trim command is not effective any more. I have no clue what that percentage really is, so if you have links or insight on this, I'd appreciate!
     
  2. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

    Joined:
    Aug 5, 2001
    Location:
    Denmark
    #2
    If it was always full, then you couldn't write to it. :p

    Trim is a standard ATA command, and works the same.

    If your SSD died in a machine, then its just a bad happening. Even if writing to it constantly, it should last many years.
     
  3. toke lahti thread starter macrumors 68000

    Joined:
    Apr 23, 2007
    Location:
    Helsinki, Finland
    #3
    You have any knowledge on how full the fusiondrive keeps the ssd part? Is there any way to track this on working fusion drive?
     
  4. toke lahti thread starter macrumors 68000

    Joined:
    Apr 23, 2007
    Location:
    Helsinki, Finland
    #4
    My ssd's death was probably manufacturing defect, it lasted less than 2 years. But that doesn't mean Trim command is useless and won't prolong ssd's life. Also optimizing how full the ssd is useful thing, according from what I have read.
     
  5. toke lahti, Dec 3, 2016
    Last edited: Dec 3, 2016

    toke lahti thread starter macrumors 68000

    Joined:
    Apr 23, 2007
    Location:
    Helsinki, Finland
    #5
    Found some info:
    http://apple.stackexchange.com/questions/90443/fusion-drive-free-space-on-ssd
    which lead to:
    http://arstechnica.com/apple/2012/1...ining-doc-ars-tears-open-apples-fusion-drive/
    "FD keeps a minimum of 4GB free on the SSD."

    So for example with 120GB owc drive, the drive itself has 7% over-provisioning, which means 9GB "outside of the volume" and FD keeps 4GB free "inside the volume" and I guess this is good enough for trim / grabage collection.
    I could also make a partition of 110GB into that ssd and use that to make FD?
    Then there would be even more free space for trim...
     

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