RAID and Trim

Discussion in 'MacBook Pro' started by cookiesnfooty, Jul 24, 2012.

  1. cookiesnfooty macrumors 6502

    cookiesnfooty

    Joined:
    Jul 1, 2009
    Location:
    Harrogate
    #1
    Hi,
    I was under the impression TRIM didn't work in RAID mode just set it up and I get the following:

    Screen Shot 2012-07-25 at 03.57.56.png

    Both drives report TRIM is active.

    Incase anyone wonders the result of setup is:

    Screen Shot 2012-07-25 at 03.29.30.png

    I am using an Early 2011 Macbook Pro 13" with 16GB RAM and thankfully both SATA ports are 6GB.
     
  2. RedRallyeZ macrumors regular

    Joined:
    Nov 15, 2010
    #2
    HA! does that say 960 mbps read times? way to make us all feel inadequate.

    very impressed, good info!
     
  3. calderone macrumors 68040

    calderone

    Joined:
    Aug 28, 2009
    Location:
    Seattle
    #3
    Apple disables TRIM if you put two of their SSDs in RAID (I have tried it). That is of course on the Toshiba drives.

    When you enable TRIM you are essentially forcing it on, all you are really doing is replacing a string within the Kext.

    The real question is: Will it work properly?

    In theory, it may not cause a problem. At the OS level, you delete a file, the OS sends the TRIM command to both drives, but of course removing only the relevant blocks on each SSD.

    Given that the RAID isn't abstracted from the OS (since it is software), it should be okay. With that said, we really don't what is happening behind the scenes.

    For example, this could go completely haywire, and the TRIM command is sent to both drives for all blocks, even blocks in which the original file was not stored inside. In other words, blocks getting erased that you don't want erased.

    I am currently running two Samsung 512GB 830s in RAID 0, with TRIM enabled. I want to run them for a bit and see what happens. If I were you, keep regular backups of your data, more ideal, if you care about your data, I would turn TRIM off.
     
  4. cookiesnfooty thread starter macrumors 6502

    cookiesnfooty

    Joined:
    Jul 1, 2009
    Location:
    Harrogate
    #4
    Thanks caldrone, I think i'll keep it on until I have an issue :)
     
  5. calderone macrumors 68040

    calderone

    Joined:
    Aug 28, 2009
    Location:
    Seattle
    #5
    I did some quick testing with dtrace, based on what I found I do not think the TRIM command is being sent at all.
     

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