Upgrading to a dual SSD (small PCIE + big SATA) Fusion Drive

Discussion in 'iMac' started by scott.n, Apr 2, 2018.

  1. scott.n macrumors 6502

    Joined:
    Dec 17, 2010
    #1
    I found an open-box deal too good to pass up on a mid-range 27" iMac last week, and am now thinking about what I'd like to do to upgrade it. It's the mid-2017 model, 3.5 GHz i5 with 1 TB Fusion Drive.

    I'm considering replacing the HDD with a 2TB SATA SSD, and then creating a new Fusion Drive with it and the existing 24 GB PCIE SSD. Has anyone done this in a recent iMac, and if so, what type of performance gains did you see?
     
  2. RyanXM macrumors regular

    RyanXM

    Joined:
    Jul 7, 2012
    Location:
    DFW, TX
    #2
    You'd be better off spending $650-700 on a 1TB Apple PCIe based SSD to replace the 24GB PCIe SSD. Search SSUBX on eBay or even SSPOLARIS. The SSPOLARIS models are going to be more expensive, but they are more in line with the controller on the 960 EVO and 960 PRO. Don't forget if you replace the 3.5" HDD in the iMac, you will need to get an inline thermal sensor so the fan does not run at full speed all the time.

    https://eshop.macsales.com/item/OWC/DIDIMACHDD12/
     
  3. scott.n thread starter macrumors 6502

    Joined:
    Dec 17, 2010
    #3
    I've read on iFixit that the external thermal sensor isn't needed since the 2012 models. Not true?

    It's much easier (and cheaper*) to upgrade the SATA drive than the PCIE drive, which is why I was thinking of just doing the latter.

    * Looking at the 2 TB Micron for ~$350.
     
  4. RyanXM macrumors regular

    RyanXM

    Joined:
    Jul 7, 2012
    Location:
    DFW, TX
    #4
    The 2012 and later do not use an external sensor. They use the internal SMART Temp sensor on custom Apple firmware for that particular hard drive, be it Seagate or Western Digital. The OWC sensor, injects the temp sensor signal into the SATA data port, where the MLB/SMC can read it.

    I can understand wanting to go the 2TB SATA 6Gbps Micron 1100 SSD. If you do that, I personally don't see the point in keeping the 24GB PCIe SSD as a swap drive. You're basically left with the OS and most used applications being on the 24GB. To each their own though.
     
  5. scott.n thread starter macrumors 6502

    Joined:
    Dec 17, 2010
    #5
    Thanks for the feedback. I misunderstood about the sensor.

    I wouldn't want to manage the 24GB and the 2TB (or whatever) as separate drives, which is why I was thinking of combining them into another Fusion Drive.
     
  6. Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #6
    Fastest, easiest, CHEAPEST, SAFEST way to get more speed:
    Buy a USB3 external SSD, plug it in, and set it up to be the boot drive.

    You'll get speeds that will be about 85% of an internally-installed SATA drive.
    But... NONE of the hassles of trying to install it.

    Get something like a Samsung t5.
    Velcro it "up and out of the way" on the back of the iMac's stand.

    Did I mention that this is the fastest, easiest, cheapest and safest way to boost its performance?
     
  7. scott.n thread starter macrumors 6502

    Joined:
    Dec 17, 2010
    #7
    Also the least fun way. I like tinkering.
     
  8. BLUEDOG314 macrumors 6502

    BLUEDOG314

    Joined:
    Dec 12, 2015
    #8
    You can do this but I have heard of issues with making fusion drives out of two ssds. I can't speak to it personally, but maybe just do OS on the 24GB drive and everything else on the other?
     
  9. nambuccaheadsau macrumors 68000

    nambuccaheadsau

    Joined:
    Oct 19, 2007
    Location:
    Nambucca Heads Australia
    #9
    Ryan is half right and half wrong. The 21.5" models do not need the heat sensor kit as Apple overcame this by using a 5400rpm notebook style drive, and made the 21.5" models with the platter drive a lemon as they are as slow as cold molasses.

    The 27" 2012 and later do need the heat sensor kit. Have a read of this from OWC. Think of what the fisho has said. A very difficult task ungluing the screen. Have told this before, a mate is a large Reseller in Sydney, Australia, and will not allow his techos to crack them. Five broken screens at $500 a pop so he now trucks them across town to Apple HQ for their technicians to work on.

    Also if this iMac came with any warranty, cracking it voids the warranty.


    https://eshop.macsales.com/item/OWC/DIDIMACHDD12/
     
  10. Samuelsan2001 macrumors 604

    Joined:
    Oct 24, 2013
    #10
    Seems like a good plan to me and if it doesn’t work well you can defuse and just use the 2TB ssd for a fast cheap machine.
     

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