Mojave on second partition, AFPS

Discussion in 'macOS Mojave (10.14)' started by TitanTiger, Jun 27, 2018.

  1. TitanTiger macrumors 6502

    Jun 8, 2009
    In the past when I've wanted to try out a new macOS version in beta, I've created a disk partition and installed it there. But with AFPS it asks me if I want to do a partition or create a new volume. I'm not quite up on the distinctions with volumes vs partitions and just wanted to ask, what should I do here? Proceed with a partition as I have in the past, or is there an advantage to using a volume instead now that I'm using AFPS? I would just like to be able to boot into Mojave to mess around a bit without affecting my main High Sierra install.
  2. eoblaed, Jun 27, 2018
    Last edited: Jun 27, 2018

    eoblaed macrumors 68020


    Apr 21, 2010
    Right now you have an APFS 'container' within which is an APFS 'volume', which is what you're booting from, using daily, etc.

    The great thing about adding another volume to that same container is that they share the usable space of the overall container. You don't need to create a new partition and go through all the headaches associated with that. You simply create a new volume in the same container.

    Example: you have a 1TB SSD, of which you're using 400GB (600GB free). You can create a new volume in that same container, and both volumes (your 'primary' one and your new/test one) have access to that 600GB of free space.

    It's almost like they're co-existing. It's pretty slick, actually.

    Here are some screenshots of my current setup.

    #1: note that when I have the physical device selected, the blue bullet point shows both 'MojaveTest' and 'Machintosh HD'

    #2: when I have the APFS container selected, you can see MojaveTest and Machintosh HD are in that same container. 269GB free for the whole container
    Screen Shot 2018-06-27 at 11.25.47 AM.png

    #3: Macintosh HD selected. You can see it's using 699GB, 269GB free. This free space is usable by both volumes in this container.

    Screen Shot 2018-06-27 at 11.26.01 AM.png

    #4 MojaveTest selected. You can see it's using 28.85GB, the same 269GB free.
    Screen Shot 2018-06-27 at 11.26.09 AM.png

    Hope this helps!
    --- Post Merged, Jun 27, 2018 ---
    I don't have to decide how to split up my storage like when adding a partition. This is huge. All volumes use whatever's available. Adding a new volume is simple, removing a volume is simple, and neither operation requires resizing of partitions or anything. Any storage needs are handed out from the container dynamically.

    I'm a big fan.

    Attached Files:

  3. treekram macrumors 68000

    Nov 9, 2015
    Honolulu HI
    You can install Mojave in the same APFS container that you have High Sierra in, provided you have sufficient space on the disk. It would create a separate volume in the container. It will size dynamically. I wrote a post on this:

    Creating a new volume for Mojave in your existing APFS container is easy and offers the flexibility of having dynamically sized volumes for High Sierra and APFS. The downside is if something goes bad with the APFS container (which has happened to some posters here on macrumors), it could affect both your High Sierra and Mojave volumes. Going the traditional route of creating a new partition on your physical disk (pressing the "Partition" button instead of the "Add Volume" button) will involve resizing your current partition and creating a new one for Mojave. That operation always gives me the chills - if you do that, do a backup before doing that.

    With how APFS works, I'm not sure how that changes the definition of volume vs. partition. I tend to think of them as synonymous but it seems "volume" is used for the separations within the container and "partition" is used for top-level separations of the disk itself.
  4. AtticusRyan macrumors newbie

    Jun 15, 2012
  5. TitanTiger thread starter macrumors 6502

    Jun 8, 2009
    Did which...the volume or the partition?
    --- Post Merged, Jun 27, 2018 ---
    Thank you for this. Question on sizing. What is "reserve" size vs "quota" size?
  6. eoblaed macrumors 68020


    Apr 21, 2010
    Googling, I find:

    "Size options allow you to set a reserve Size; this is the minimum size the volume will have. Enter the Reserve Size. The Quota Size is used to set the maximum size the volume is allowed to expand to. Both values are optional, if no reserve size is set, the volume will only be as large as the amount of data it contains. If no quota size is set the volume only size limit will be based on the container size and the amount of space taken up by other volumes within the same container. Remember, the free space in a container is shared by all volumes within."

    I don't recall fiddling with those options at all when I created my MojaveTest volume.

    - scott
  7. TitanTiger thread starter macrumors 6502

    Jun 8, 2009
    Thanks for everyone's help. Went with the volume instead of partition. Everything looks good.
  8. eoblaed macrumors 68020


    Apr 21, 2010
    Isn't the whole APFS volume thing awesome? :D
  9. TitanTiger thread starter macrumors 6502

    Jun 8, 2009
    Yeah, that's much quicker and simpler than partitions.
  10. eoblaed macrumors 68020


    Apr 21, 2010
    Not to mention more flexible. The whole thing about not having to commit to certain fixed sizes for partitions is very freeing.
  11. ChrisChaval macrumors 6502


    Aug 30, 2016
    Thank you guys

    Installing Mojave right now on an APFS volume just to see if I like it

    While keeping my High Sierra installation

    Easy to revert back or switch back and forth

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10 June 27, 2018