iMac 21.5 late 2012 installation of SSD

Discussion in 'iMac' started by Sebski, Nov 19, 2016.

  1. Sebski macrumors member


    Oct 8, 2016
    Dear All,

    I have an iMac 21.5" late 2012 version (iMac13,1), 2.7GHz with 1TB Fusion Drive. I'm planning to do an upgrade and 'break' fusion drive to install new SSD drive in place of standard HDD drive. It's just to slightly refresh my machine, I think I'll keep it for another 1-2 years hence this decision.

    I was looking on many forums but can't really find answer to this question: can I replace SSD part of fusion drive in my model of iMac? I found some upgrade-kits on different websites, for example on OWC, but there's always a note saying it's not compatible with 21.5" 2.7GHz Late 2012 model. I'm assuming this refers to models shipped only with standard HDD drive. Am I right? If I am right then what connector is it? It it m2?
    I was thinking to replace this SSD with a bigger size SSD to use it as a boot-up system disk. And then replace HDD drive with SSD and have two separate disks.

    Now, if replacing existing SSD drive is not possible or too expensive (also saw on iFixit that it's actually more complicated than replacing HDD only) then I'd be happy to only replace HHD drive with SSD (min. 512GB) and use the new SSD as a boot-up system disk, and keep existing-old 128GB 'Apple' SSD as a second, separate disk. I wonder if performance of SSD drive will still be as good after 1-2 years as after first installation. I was reading about TRIM support and to be honest couldn't find any conclusive answer. So how is it with 3rd party SSD's on macOS? Is TRIM supported automatically out-of-a-box? Am I risking a significant performance decrease when I use the new SSD as a boot-up disk?

    Please, every advice will be much appreciated.

  2. Fishrrman macrumors G5


    Feb 20, 2009
    My opinion will be different from just about everyone else's here, but...

    ... what you're planning to do doesn't make any sense.

    First of all, I believe the "SSD portion" of the fusion drive that's already in the iMac uses a non-standard form factor and connector.
    You -can't- just buy another SATA SSD and replace it that way.

    May I ask what is -wrong- with the iMac (in terms of drive performance) right now, that makes you wish to change it?
    Is it not fast enough?
    Is there not enough space?

    If all you want is a "bigger" SSD boot drive, do this:
    1. Buy an EXTERNAL USB3 SSD such as one of these:
    2. Plug it into a USB3 port and initialize it using Disk Utility.
    3. Install a copy of the OS onto it. You can then either:
    a. install a completely "clean" install, or
    b. use CarbonCopyCloner to "clone over" your existing OS.
    4. Set up the Startup Disk pref pane so that the external is the boot drive.

    Use the internal fusion drive for general storage or whatever you wish.

    Also -- are you absolutely sure of your confidence and ability to open an iMac and do surgery? Many folks have thought they could do it, and then, opened it up, and.... broken something inside.

    Adding an external SSD is the best option -- fast, easy, performance will be at least 80% of that of an internally-mounted drive (not enough to notice much difference).
  3. Sebski thread starter macrumors member


    Oct 8, 2016
    Thank you for your opinion Fishrrman. I use around 250-300GB of data on a daily basic - I mean, I don't process the same 250-300GB of data every day but I have this amount of data in apps and files and I use it over and over (data that is not needed to be used daily is stored on external drives). Having only just over 120GB of SSD space I can see that it doesn't operate as smooth as when I had only small data which was within limit of SSD capacity. That's why I wanted to get 512GB (minimum) of SSD as my main drive.

    I'm confident enough to replace existing HDD drive with SSD. I know that getting to SSD part in this iMac is a bit more tricky that's why I mentioned that this is one of the options. In the past I did some surgery on previous iMac models and also few MacBook including completely taking apart a MacBook Pro few years ago. I know I have to be more careful now, opening/un-glueing screen but I am definitely able to do this.

    I just wonder if anyone have any bad experience with using 3rd party SSD's in OS X (macOS) as a main boot-up disks.

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