Late 2015 2.5" SSD Replacement for Fusion Benchmarks

Discussion in 'iMac' started by Photios, Apr 20, 2016.

  1. Photios macrumors member


    May 17, 2009
    I've got a Late 2015 iMac, 4.0ghz i7 with a 2TB Fusion drive. I purchased an external Dual drive Thunderbolt 2 enclosure, which houses a 1TB Samsung 850 EVO for booting, and a 6 TB 7200 drive for data. I'm actually fairly happy with the Thunderbolt enclosure as far as speed is concerned. I'm getting roughly speeds of 490 MB/s write and 525 MB/s read using Blackmagic. My 3.5 hard drive is getting speeds of 172 MB/s write and 165 MB/s read (strange as the write is faster than the read). These speeds are appreciably faster than my 2010 Mac Pro.

    Anyway... my question is that if I were to replace my internal fusion drive with the samsung SSD... would I see any more speed increase in reads and writes? Has anyone done this and posted benchmarks with Blackmagic?
  2. Tavicu, Apr 21, 2016
    Last edited: Apr 21, 2016

    Tavicu macrumors regular


    Jul 25, 2013
    If you mean the speed inside vs over thunderbolt, nope, don't think it will make a difference. And even if there will be a difference, it will be very small!
  3. maflynn Moderator


    Staff Member

    May 3, 2009
    The Fusion drive is a logical joining of two physical drives, one being a Flash drive, and the other a spinning drive. If you replace the spinning drive, you'll receive SSD speeds and yes, the increase in performance will be noticeable. 2015 iMac models however are virtually sealed, and cracking them open is not for the faint of heart, nor would it be something that is worth risking your warranty for..
  4. mpe macrumors 6502

    Sep 3, 2010
    The Samsung 850 EVO will be connected on 6Gbit/s SATA as opposed to much faster PCIe-connected SSD portion of the Fusion. That will lower the benchmarks.

    Replacing the HDD part of the Fusion will give you two de-fused standalone drives - 128GB and the new 1TB SSD.

    If you run benchmarks on the 1TB drive they will most likely show lower scores as soon as test file size stays below the threshold of the fusion drive. Same for real world use cases.

    The practical difference will be negligible though unless having a special use case.
  5. dimme macrumors 65816

    Feb 14, 2007
    SF, CA
    Which Dual drive Thunderbolt 2 enclosure did you purchase. Is it fanless? If not how quiet is it?
  6. Photios thread starter macrumors member


    May 17, 2009
    That's exactly what I was thinking... not much difference. I'm happy with the performance though... roughly 33% faster than using an external USB enclosure.
    --- Post Merged, Apr 21, 2016 ---
    I purchased the Akitio Thunder2 Duo Pro. It was more expensive than what I wanted to spend, but the reviews were extremely positive, and I figured that now I have switched from a mac pro, this is a necessary expense for backups and data, let alone so I can boot from an SSD if I don't want to use the fusion drive. I'm considering getting another and then setting both up in a raid configuration for greater speed. The Thunder2 has a fan, and it is very quiet. I have the fan on because I do have the 3.5" drive installed in it, but you have the option of turning it off. I also have the drive located on the floor behind my desk. The Thunderbolt cable that was included is a meter long, so I needed to get a 2m cable, to allow me to not worry about the possibility of the cable being extracted out of the iMac or drive enclosure if one of my kids decides to move the iMac for a different viewing angle one way or the other.
    --- Post Merged, Apr 21, 2016 ---
    That's the whole thing right there... does cracking it open void the warranty? One would think so. Huge incentive to just live with it and work around the limitations.

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