Installing MacOS on external USB 3 SSD

Discussion in 'macOS' started by mrochester, Jun 22, 2017.

  1. mrochester macrumors 65816

    Joined:
    Feb 8, 2009
    #1
    Hi all

    I was looking at an iMac but perhaps getting one with a standard hard drive and then using an external USB 3 connected SSD to install MacOS onto.

    Does anyone have any experience of how well this will work? I understand that there is a theorietical maximum throughput for USB 3 that you rarely achieve but would this impact performance significantly? The thing I appreciate most about SSDs is the reduced latency rather than the increased throughput so would USB 3 impact this to make it not worthwhile?

    Many thanks

    M.
     
  2. BrianBaughn macrumors 601

    BrianBaughn

    Joined:
    Feb 13, 2011
    Location:
    Baltimore, Maryland
    #2
    I assume you mean the 21.5 inch iMac without a fusion drive.

    The drive is the slowest thing on a computer these days and there's really no excuse to be running the system on anything other than an SSD (or at least a fusion drive) connected to the fastest available bus on the unit.

    It seems like the cheapest iMac available is never a great choice.
     
  3. keysofanxiety macrumors 604

    keysofanxiety

    Joined:
    Nov 23, 2011
    #3
    It'll work very well. SSD real-world performance boost predominantly come from the instant access times, so a slight deficit in read/write speeds won't have much noticeable effect, especially if you're used to HDD performance!

    Also couldn't be easier to set up:

    1) plug in SSD via USB
    2) hold CMD + R on startup
    3) format SSD in disk utility
    4) select reinstall macOS & point it to the SSD
    5) laugh maniacally at the ease of drastically improving system performance (optional)
     
  4. Fishrrman macrumors G4

    Joined:
    Feb 20, 2009
    #4
    OP wrote:
    "I was looking at an iMac but perhaps getting one with a standard hard drive and then using an external USB 3 connected SSD to install MacOS onto."

    My advice is "don't do this".
    Spend $100 more and get the iMac with the 256gb SSD (you have to do this through "build to order").

    The internal SSD will be 4-5x faster than any external SSD. VERY fast.

    I recommend booting from an external SSD for older Macs, but the new iMacs have such a great internal SSD it's the best option.
    And did I mention that you can get the 256gb version for only $100 more?
     
  5. SaSaSushi macrumors 68040

    SaSaSushi

    Joined:
    Aug 8, 2007
    Location:
    Takamatsu, Japan
    #5
    I need to get a weather report for hell because it's gotta be snowing there today. :)
     

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