TRIM on a Fusion Drive

Discussion in 'Mac mini' started by jjk454ss, Feb 21, 2013.

  1. jjk454ss macrumors 601

    jjk454ss

    Joined:
    Jul 10, 2008
    #1
    Not sure what I thnk might happen, but it is OK to use TRIM Enabler on a SSD that is setup as a Fusion Drive with a 1 TB HDD right? I'm just thinking because the Fusion drive moves blocks around and TRIM moves blocks around I don't want to mess things up.
     
  2. Designed4Mac macrumors 6502

    Designed4Mac

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    Jan 6, 2013
    Location:
    I Wish I Knew
    #2
    Finally got round to doing mine on Wednesday. Apart from what i thought were crap tools from OWC (luckily i had my own) everything went fine and all is now up and running.
    The first thing i done after installing everything was enable Trim. All seems to be working ok except smart only shows hours and power cycle count for SSD and temp,power and cycle for HDD.
    As there seems to be nothing at the moment that tells me its doing any harm i'll leave it running for now.
     
  3. jjk454ss thread starter macrumors 601

    jjk454ss

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    Jul 10, 2008
    #3
    Thanks. And glad you finally for the kit and got it done.:D
     
  4. sfxguy macrumors member

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    Oct 14, 2011
    Location:
    Los Angeles
    #4
    Anyone find that it is worth it to enable trim on a new diy fusion drive in a 2012 mini?

    If so are you using trim enabler to do it or something else?

    I see there is an option to enable trim in Mountain lion tweaks, under the Lion tab.

    Just wondering if its really needed and maybe it's better to just leave it off.

    Thanks
     
  5. dangerly macrumors regular

    Joined:
    Oct 27, 2009
    #5
    I believe you should enable TRIM always, SSDs are dum in respect to HDDs. What i mean is that SSDs don't know which and where blocks are free or used, only way is to enable TRIM. It will guarantee good performance in time, otherwise after some time SSDs will slow down and degrade performance.
    Just use TRIM enabler, it works fine.
     
  6. tomjleeds macrumors 6502

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    Jul 19, 2004
    Location:
    Manchester, UK
    #6
    This is not because SSDs are dumb. Spinning disks do not know which blocks are free or used either - this is why you have a file system :rolleyes:
     
  7. dangerly, Feb 28, 2013
    Last edited: Feb 28, 2013

    dangerly macrumors regular

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    #7
    SSDs are actually dum as compared to HDDs. During write/delete operations they accumulate all sorts of garbage, becoming slower and slower. HDDs keep track of every single sector on their platters and keep a map of them, since they have access to the file system structures, including the list of unused clusters. SSDs don't have access to the file system structures. The quote below is not from me but from Wikipedia
    (http://en.wikipedia.org/wiki/TRIM):

    "In computing, a TRIM command allows an operating system to inform a solid-state drive (SSD) which blocks of data are no longer considered in use and can be wiped internally. While TRIM is frequently spelled in capital letters, it is a command name, not an acronym.

    TRIM was introduced soon after SSDs started to become an affordable alternative to traditional hard disks. Because low-level operation of SSDs differs significantly from hard drives, the typical way in which operating systems handle operations like deletes and formats (not explicitly communicating the involved sectors/pages to the underlying storage medium) resulted in unanticipated progressive performance degradation of write operations on SSDs. TRIM enables the SSD to handle garbage collection overhead, which would otherwise significantly slow down future write operations to the involved blocks, in advance."
     
  8. xlii macrumors 68000

    xlii

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    Sep 19, 2006
    Location:
    Millis, Massachusetts
    #8
    Have there been any tests between a system with trim enabled and one without trim enabled to show what kind of a benefit trim gives? If anyone has a pointer to that...
     
  9. dangerly macrumors regular

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    Oct 27, 2009
    #9
  10. Giuly, Feb 28, 2013
    Last edited: Feb 28, 2013

    Giuly macrumors 68040

    Giuly

    #10
    Yeah, no.
    The problem is that NAND cells can only be written when they're empty, and if you read them to determine whether they're empty or not and then maybe empty them during the write operation to the SSD instead of in the background while idling by issuing TRIM commands and marking them as known empty in teh map, writing gets slow.
    Hard drives don't care because they don't know empty, just 0 or 1.
     
  11. TinHead88 macrumors regular

    TinHead88

    Joined:
    Oct 30, 2008
    #11
    TRIM is not recommended (may even degrade performance or cause issues) on Sandforce controllers.

    Many SSDs do their own garbage collection and TRIM is simply not beneficial. Do some research on yours!

    Perhaps an analogy is when people accidentally run 2 Windows programs that do the same system tasks like virus protection, etc. That causes all sorts of problems.
     
  12. tomjleeds macrumors 6502

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    Jul 19, 2004
    Location:
    Manchester, UK
    #12
    You are completely wrong. Utterly, totally, 100% wrong. Quoting swathes of Wikipedia does not change that. You should really learn what you are talking about before spouting bollocks.

    The difference in behaviour is due to the technology, as outlined by Giuly.
     
  13. dangerly macrumors regular

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    Oct 27, 2009
    #13
    Correct.
    So what did i write so wrong?
    Aren't we stating the same thing but with different words/explanation?
     
  14. tomjleeds, Mar 1, 2013
    Last edited: Mar 1, 2013

    tomjleeds macrumors 6502

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    #14
    This bit:

    They don't "accumulate garbage", they are slowed because an overwrite of a non-empty block requires an extra "erase" step before writing. This is in contrast to a HDD which just overwrites the block straight off.

    TRIM informs the disk about unused blocks, yes, but this is not because SSDs are dumb and HDDs are smart.

    EDIT: My previous response was a bit unfair, apologies.
     
  15. MatthewAMEL macrumors 6502

    MatthewAMEL

    Joined:
    Oct 23, 2007
    Location:
    Orlando, FL
    #15
    TRIM is recommended on EVERY SSD chipset. If you have an SSD with a SandForce controller, make sure you have rev 5+ of the firmware. Your SSD manufacturer may renumber/version the firmware, find out if the current version is based on Version 5 from SandForce.

    Newer versions of the SF controller (i.e., SF-2281) support TRIM and e7h (Flush Cache) command with the initial release of the FW.

    Garbage Collection and TRIM are not the same thing. Garbage Collection is a hardware level function. TRIM is a SATA command that is passed to the drive from the OS.
     
  16. PinoyAko macrumors 6502

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    Nov 25, 2012
  17. dangerly macrumors regular

    Joined:
    Oct 27, 2009
    #17
    A non empty block can be defined as a block partially occupied by garbage?
    If SSDs need to be informed about unused blocks makes them less "wise" than HDDs., that's what i meant in saying that SSD's are dumb in respect to HDDs.
    Thanks for the apologies, no need for them.
     
  18. tomjleeds macrumors 6502

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    Location:
    Manchester, UK
    #18
    I suppose you could argue that way, to me garbage is something a bit different but your definition is probably reasonable - now that it has been qualified!

    SSDs have a technical limitation when it comes to overwriting already-used blocks, which HDDs don't have. Describing this as HDDs being wiser than SSDs or SSDs being dumber than HDDs just doesn't work. I can see where you're coming from but your chosen words are misleading.
     

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