SSD speed question: 2017 iMac with Samsung EVO 850

Discussion in 'iMac' started by NervousFish2, Jun 1, 2018.

  1. NervousFish2 macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
    #1
    Good people.

    What speed should I be getting on my 2017 27" iMac with the original Fusion Drive removed, and replaced with a Samsung EVO 850?

    The guy who did it for me took out the Seagate HD, and left in the 128 gig "SSD" bit of the hybrid.

    But there is a massive difference between the remaining Flash part of the Fusion Drive, and the EVO SSD!

    According to Blackmagic, the 128GB Fusion flash drive gets:
    Write: 753
    Read: 2445

    While the Samsung 850 EVO gets:
    Write: 463
    Read: 504

    I just want to know if this is normal, or if there's something I need to get fixed.

    Thanks!

    Nick
     
  2. estabya macrumors 6502

    estabya

    Joined:
    Jun 28, 2014
    #2
    This is normal. The 128GB SSD uses a PCI-E interface that has a significantly higher bandwidth than the 6Gbps of the SATA3 interface that the 850 EVO is using.

    In real world use you’d be hard pressed to tell the difference between the two anyway.
     
  3. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
    #3
    Gotcha. Thanks. "Real world" in this sense being boot time, app start up, converting large files in GarageBand or occasional video work?
     
  4. jerwin macrumors 68020

    Joined:
    Jun 13, 2015
    #4
    To quote Samsung's Marketing:

    http://www.samsung.com/semiconductor/minisite/ssd/product/consumer/850evo/

    and here some benchmarks for flash storage:

    http://barefeats.com/imac2017_storage.html
    [​IMG]

    [​IMG]

    It's possible the 128 GB flash unit has lower write speeds because a higher write speed doesn't improve fusion drive performance (and is available at lower cost).

    It's also a different benchmark. The fixes for SPECTRE/Meltdown may also limit I/O speed.
     
  5. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
  6. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
    #6
    Hey folks,

    Just returning to this topic again briefly. In your opinion, would it be better for me to boot the OS off the PCI-E drive? And use the EVO for files? Or do you have thoughts about the best way to optimize my use of that drive? Would it make much a 'real world' difference to keep the OS and the apps on the PCI-E? I know one of you was saying above maybe it wouldn't, but I just want to be clear in my understanding.

    Thanks,

    Nick
     
  7. eoren1 macrumors 6502

    Joined:
    Aug 17, 2007
    #7
    This is what I have - boot OS is on internal super fast SSD. Home Directory on the external Samsung 850 EVO. Works great. No issue with either getting too full but definitely would have hit space constraints if kept all on internal 500gb drive
     
  8. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
  9. OldMike macrumors 6502

    OldMike

    Joined:
    Mar 3, 2009
    Location:
    Dallas, TX
    #9
    I don't think, in most cases, you will be able to tell the difference between the two drives. I have posted this before, but every time I look at the numbers, it is always surprising.

    Here is a test of a 960 EVO SSD drives with max throughput of 3200 MB/s read and 1500 MB/s write, compared to an 850 EVO SSD with read/write speeds of about 500 MB/s in real world terms:

    Windows 8.1 Boot time:
    Samsung 960 EVO ~ 15.3 seconds
    Samsung 850 EVO ~ 15.5 seconds

    790 MB 4K video load time:
    Samsung 960 EVO ~ 6.5 seconds
    Samsung 850 EVO ~ 6.5 seconds

    523 MB GIMP image load time:
    Samsung 960 EVO ~ 8.3 seconds
    Samsung 850 EVO ~ 8.5 seconds

    159 MB Project opened in Visual Studio containing source code for LLVM toolchain:
    Samsung 960 EVO ~ 6.5 seconds
    Samsung 850 EVO ~ 6.5 seconds

    These figures are from the following article:
    https://techreport.com/review/30993/samsung-960-evo-ssd-reviewed

    I would be very happy to use the Samsung 850 for everything. In the past I have even run my Macs entirely off of an external Samsung 850 and have been very happy with the performance. If you might ever need to use Windows, you can always save the 128GB SSD for bootcamp.
     
  10. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
    #10
    Thank you. This is also very helpful. One of the reasons I asked was that, to me, it seemed the Samsung was booting slower than the PCI-E/fusion drive. Which surprised me.

    If you don’t mind, one quick question about installing Bootcamp on that PCI-E drive. What’s the best way to do it? Its been giving me a headache trying to do it, the last week or so. I’m away from my desktop right now, but does that drive have to be formatted for NT before you try to install bootcamp?
     
  11. PortableLover macrumors 6502a

    Joined:
    Apr 14, 2012
    Location:
    england
    #11
    860 for OS, 970 evo for work files. I am not sure if Garageband could take advantage of a pcie drive vs a sata drive since Idont use any audio apps. The thing is with sata is that is more then enough for a OS.
     
  12. NervousFish2 thread starter macrumors regular

    NervousFish2

    Joined:
    Mar 23, 2014
    #12
    Thank you. I do spend a lot of time in GarageBand so speed there certainly a factor.
     
  13. OldMike macrumors 6502

    OldMike

    Joined:
    Mar 3, 2009
    Location:
    Dallas, TX
    #13
    I apologize for the misinformation. I haven't used Bootcamp in a long time (I have a dedicated Windows machine now). It appears that bootcamp needs to be on a partition on your MacOS BOOT drive, which is unfortunate if true.

    According to Apple:
    Boot Camp Assistant guides you through installing Windows on your Mac. Open this app from the Utilities folder inside the Applications folder. Then follow the onscreen instructions to repartition your startup disk and download related software drivers for Windows. If you're prompted during installation, connect a blank USB 2 flash drive.

    This is from: https://support.apple.com/en-us/HT201468

    An alternative, and perhaps even better solution (if you don't need graphics performance) would to be use Virtual Box to install a Windows VM (or buy VMware or Parallels). Then you could just format the 128GB SSD as a MacOS drive and keep the virtual image there.
     
  14. tubeexperience macrumors 68040

    Joined:
    Feb 17, 2016
    #14
  15. T'hain Esh Kelch macrumors 601

    T'hain Esh Kelch

    Joined:
    Aug 5, 2001
    Location:
    Denmark
    #15
    I am by no means an expert on GarageBand, but I would be surprised if you could feel much of a difference. Aren't all the files loaded relatively small, and the real processing going on, mainly CPU bound?
    --- Post Merged, Jun 10, 2018 ---
    I think those 1-2% differences is well within margin of error. Modern SSD's are all bottlenecked by a SATA6 connection.
     
  16. Fishrrman macrumors P6

    Fishrrman

    Joined:
    Feb 20, 2009
    #16
    Those speeds look to be right where they should be.

    Take a really good look at the differences between the Apple 128gb SSD drive (that was originally part of the fusion drive) and the Samsung SSD.

    Reads almost 5x faster and writes about 45% faster.

    This is why I've posted here again and again that the best solution for a 2tb fusion drive iMac is to de-fuse the two internal drives and set up the SSD as the boot drive, and run it that way.
     

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