Is anyone running a 2018 Mini from an external SSD

Discussion in 'Mac mini' started by DYER, Dec 21, 2018.

  1. DYER macrumors 6502

    Oct 4, 2008
    London, UK
    Hi everyone,

    It's been ages since I've bought a new Mac, in-fact I'm currently only running an old Mac Mini that is starting to show its age.

    My question to you, is whether anyone is running a new 2018 Mini from an external SSD. I can't justify Apple prices when I can get a good quality 2TB SSD for £250 including a USB C enclosure.

    If anyone has done this, what kind of performance hit are you taking vs the internal drive.

    And to those of you that understand everything a little more than me, would a better setup be to use a 256GB internal drive to boot and use the 2TB drive externally or just run the whole system of the 2TB external drive and ignore the internal one? My reason for ignoring the internal drive is just simplicity of not having to 'manage' my storage as much.

    Look forward to hearing your thoughts.
  2. thirdsun macrumors member

    Nov 16, 2018
    You should definitely boot from the internal drive. Unless you’re buying some high end external NVMe SSD, the internal SSD will almost certainly be significantly faster and easier to setup. Having to manage your storage is the much smaller downside in my opinion.
  3. DYER thread starter macrumors 6502

    Oct 4, 2008
    London, UK
    Ah OK, that's good to know. Didn't realise the speed difference would be that great.

    Might need to upgrade to the 512GB version and then just use the 2TB and manage the files. I was considering just getting a Drobo and saving media to that as my external drives are getting messy anyway.

    I don't mind booting from external and setting it up, I did so with my current Mini for a while but it sounds like I'd be missing out on significant performance gains if I followed my current model.
  4. Spectrum macrumors 65816


    Mar 23, 2005
    Never quite sure
    256 GB internal (even the 128 GB internal) is likely to be plenty for just a boot drive.
    Then set it up so that your entire home folder is on the 2TB external.
  5. megaseppl macrumors member

    Dec 20, 2013
    Put your user directories onky on the external drive. I'm doing it and it works well.
    Just log in with a user with administrative permissions you do NOT use regular (like 'admin') right-click your normal user account in the system prefs Users & Groups, change user directory path to your external drive - that's it.
    All Applications and the System keep on the internal drive, directories like Documents, Fotos etc. go to your external drive.
    - It's best if you do it before the first login with the main user account.
    - Don't change the name of the external drive after it. (In Finder it's not possible anymore, but in Disk Utility it is.... but it would destroy the path so you have to fix it again)
  6. Fishrrman, Dec 21, 2018
    Last edited: Dec 23, 2018

    Fishrrman macrumors P6


    Feb 20, 2009
    Next-to-nobody on this board has as much experience in booting and running a Mini from an external SSD as do I.

    I've been booting and running my 2012 Mini from an SSD in a USB3/SATA dock since the day I took it out of the box in January 2013. It still runs great -- writing this reply on it now.

    HOWEVER ---
    I will advise you to FORGET ABOUT DOING THIS with the 2018 Mini.
    Boot it from the INTERNAL SSD, instead.

    The internal SSD on the 2018 Mini's is far far FAR faster than almost ANY external SSD you can hook up to it.
    (The exception will be thunderbolt3 SSDs with nvme drives inside, but... these are almost as expensive as paying Apple for the internal storage.)

    YES, you do want to buy and use an external SSD as well for additional storage.
    You should even keep a bootable partition with a copy of the OS on it, for emergencies. This is good operating practice.

    I'd recommend a Mini with either 256gb or 512gb for the internal SSD.
    256 is fine if that's all you want to spend, it will have plenty of room and it will be VERY fast for the setup I describe next.

    Set things up this way:
    - Keep the OS, apps, and your "basic" accounts on the internal SSD
    - Use external supplemental storage for "large libraries" -- movies, music, pics, etc.

    The idea is to keep the boot SSD "lean and clean", with plenty of extra space for VM swap files and application "temp" files.

    Managing more than one drive on the desktop is child's play.
    You'll get used to it quickly, and you'll know "where things are supposed to go"...
  7. DYER thread starter macrumors 6502

    Oct 4, 2008
    London, UK
    Thanks - this is really useful information - appreciate it!

    Also very useful, thanks, I hadn't really thought about SSD beyond SSD rather than in the context of NVME.
  8. leo-tech, Dec 24, 2018
    Last edited: Dec 24, 2018

    leo-tech macrumors regular


    Sep 23, 2017
    Just of curiosity, I wonder what would be the best way to minimize read/write operations on internal SSD?

    I'm thinking about shifting most or all all read/write operations to external SSD instead, with the sole purpose to enhance the lifespan of Mac Mini 2018.

    However, even if I boot macOS from external SSD, it will still perform a certain amount of read/write operations on internal SSD - so the real question here is "can the internal SSD be switched off completely?" (speed is not the issue, as for my purposes external TB3 SSD can be reasonably fast).
  9. Synchro3 macrumors 68000


    Jan 12, 2014
    You can ignore the internal one if you enable 'external booting' in the T2 security settings:


    I've set up an external M.2 SSD via Thunderbolt, slightly slower than the internal SSD:
  10. Fishrrman macrumors P6


    Feb 20, 2009
    leo asks:
    "Just of curiosity, I wonder what would be the best way to minimize read/write operations on internal SSD?"

    The best way to prevent a lot of needless reads/writes is to DISABLE VM "disk swapping".
    This will end all the "page-outs" and "page-ins" that VM makes when updating the VM swap file.

    There are some provisos to doing this, however:
    - You need enough physical RAM so you can run things without exceeding the capacity of your physical RAM
    - you need to "keep a close watch" over what's running, and how you use the physical RAM that you have.

    I've been running my 2012 Mini this way for a few years now. It has 10gb of installed RAM (1 2gb DIMM + 1 8gb DIMM).
    No crashes, runs fine.

    To disable VM swapping, use this in terminal:
    sudo launchctl unload -wF /System/Library/LaunchDaemons/

    To check if VM is being used:
    sysctl vm.swapusage
    If VM is off, report should be:
    vm.swapusage: total = 0.00M used = 0.00M free = 0.00M

    To remove the swap file:
    sudo rm /var/vm/swapfile*
    (I think the command above is right)

    To RE-ENABLE virtual memory:
    sudo launchctl load -wF /System/Library/LaunchDaemons/

    The above commands work for me using Low Sierra and HFS+.
    Not sure if they remain the same for more recent versions of the OS, or for boot volumes running APFS...
  11. japtor macrumors regular

    Jun 29, 2010
    If you don't boot off it and don't use it for anything the writes will be so minimal as to be negligible as far as life of the flash (and reads don't matter). But to answer the question, if you boot off an external I think you should be able to unmount the internal cause nothing will be using it.

    If you want to boot off of it the only things I can think of are to do stuff like the above (disable VM) or move stuff off the disk, in effect slowing down performance. Main thing is to move the users off (which is easy enough), the rest of the action would be in VM and caches and logs and other temporary files. Might be tricks to move or limit that stuff, but again it'd be at the cost of performance (you want that stuff on the fastest storage).
  12. bigfatipod macrumors regular

    Sep 22, 2011
    Any recommendations on how to go about migrating down from a 2tb SSD to a 256/512gd internal? Would using the OS that comes installed on a 2018 and then using migration assistant to bring over apps, but not music/photos, be an option?
  13. Fishrrman macrumors P6


    Feb 20, 2009
    fatipod wrote in 12:
    "Would using the OS that comes installed on a 2018 and then using migration assistant to bring over apps, but not music/photos, be an option?"

    Yes, that's pretty much how to do it, but...

    DON'T wait and use migration assistant.
    Instead, use "setup assistant" when you first power up the new Mini.

    Do you have a way to get that 2tb of "stuff" onto an external drive?

    I STRONGLY SUGGEST creating a cloned backup using either CarbonCopyCloner or SuperDuper BEFORE you unpack and set up the new Mini.

    Then, do this...
    - take new Mini out of the box, set it up, but DO NOT press the power on button yet
    - connect your cloned backup
    - NOW press power on, let the new Mini "come alive"
    - begin setup
    - at the appropriate moment, setup assistant will ask if you wish to import from another Mac or drive. YES you WANT TO DO THIS.
    - "aim" setup assistant at the external cloned backup. Give it some time (may take a few minutes) to "digest things". BE PATIENT.
    - setup assistant will now present you with a list of stuff available to be "migrated over" (including apps, accounts, settings, data)
    - NOW THINGS GET IMPORTANT. You need to go into the accounts area and DE-SELECT the "large libraries" (movies, music, pics). Perhaps some data folders, too (depends on WHERE you keep your data).
    The idea here is to "leave this large stuff" behind, but bring the important stuff over.
    - When you've got it as you like it, let setup assistant do its thing. Again, BE PATIENT. It's going to take some time. Maybe even hours.
    - When done, you should be presented with a login screen for the new Mini.
    - Login, and "look around" to see if things are as you want them. You're going to need to open and test every 3rd party app, to see if updates are needed.
  14. bigfatipod macrumors regular

    Sep 22, 2011
    great info. That’s part about de-selecting libraries sounds like it’s what I need to focus on.
    The drives are currently internal SSDs in my 2012, but they’ll turn into external ones with a 2018 model. Thanks!

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13 December 21, 2018