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macrumors 68020
Original poster
Oct 21, 2005
Is there any reference or overview to be found somewhere of how much disk space the various MacOS/OSX versions take up?
And also which disk format (HFS, APFS etc.) each OS uses.

I occasionaly need to run some software which doesn't run on my current OS (10.14 Mojave -which is the latest OS I can run on my mid-2010 Mac Pro, at least officially), and it would be great to dedicate a spare hard drive or SSD to multiple OSes so I can choose to boot into the required one whenever I need to run an "outdated/unsupported" app without too much hassle. Partition the drive into say 5 parts, then install 5 different MacOS versions on each of their own partition.
Obviously I also need to take into consideration the disk space needed for any apps running within a certain OS, and some work-space as well.

I suppose transferring the finished file(s) back to my regular working environment would be a matter of storing them on a user's "Public" folder, or are there other better ways to do it?


macrumors regular
Sep 9, 2020
There is no accurate data for this question as it varies from device to device. As Monterey for example, macOS takes 15.42GB but the system data takes 80.75 GB and this number will go up steadily. You should have at latest 100GB to run Monterey!
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macrumors 68020
Original poster
Oct 21, 2005
I should probably first decide on which OS versions to use and take it from there.
Is it possible to "resize" a partition later if I should find out that I don't have enough space for a given OS and its apps? I remember this being possible with Boot Camp, but don't know if it's generally possible within MacOS using Disk Utility or something...

I don't think I need much storage space for the apps and files I'm working on as this will just be for temporary work -not file storage. I've got a spare 128GB SSD which I can use for all this, and I think I'd install 10.6 (Snow Leopard) and 10.9 (Mavericks) on it first of all.
Possibly also 10.15 (Catalina) and if possible one of the newest OSes (the latter for having the ability to buy/download apps from the App store which are no longer officially available for compatibility with older OSes, but once downloaded there I can boot into my current, much older OS (10.14 Mojave) and have the option to download the latest version for that OS).
For 10.15 and the more recent OS I believe I might need to resort to some sort of patcher, so it won't be as straight forward as with the other, older OSes, so I'm looking forward to getting it all over with.

If there's enough room it would be nice to install Windows 10 on a partition on that same drive, but I recall there being some issues of corrupting the BootROM of older Mac Pro machines (I'm on a mid-2010 Mac Pro) if you install it on an SSD (as opposed to using a hard drive), so I need to look into that first.
But from what you guys say here it might not be possible to put all that on a 128GB SSD, so maybe I need to install the later MacOS versions on a separate hard drive instead.


macrumors member
Nov 18, 2021
While attempting to install an OCLP and getting confused I heard that it was possible to get a copy of the current OS on the same Flash drive; the advice from Apple was that 14GB was req'd - 14.09 was available; Bing Chat indicated that it should work and for a while I was in fantasy mode. Of course in execution the msg. came up that it needed at least another 8.9GB; I vaguely understand that there is a difference between volume/space of files and that taken up on disk but not a 60% or so variation. Anyway just to point out that without expert understanding of the secret language then there is guesswork involved. I recall with an install of Windows 10 that I think twice I created enough space on the disk in accordance with its precise looking figures that presented but again and again it came up with a new and higher figure. That stated my recent "advice" from Apple is that with about 41GB available I could have Sonoma OCLP and Monterey on the same flashdrive (and with different formatting for each partition - apparently.)


macrumors 65816
Sep 1, 2021
It is possible to have a single flash drive containing all available macOS installer provided that it has enogh space...

I have a 32GB flash drive with 10.10, 10.11, 10.13, 10.15 on it... 10.12 and 10.14 on separate 8GB flash drives...

It is not possible to resize the partition once you have set up Boot Camp so you need to make sure to allocate enough space for both...

I initially partitioned the empty internal drive using Yosemite Disk Utility however it is not using GPT so I had to erase and repartition using Catalina (anything post-Yosemite should work) Disk Utility and I was able to install Windows 10 64bit on the other partition...

I did not use the Boot Camp utility from within macOS... I downloaded the Boot Camp drivers using Brigadier from github... This seems to only work on macOS or Windows installed on an actual Mac... I tried on a Windows hardware but it did not work... I have not tested it on a Hackintosh...

Some apps require macOS 13.x before you can download and install from the Mac App Store... You just need to check first the compatibility of the apps then download them as much as possible using the latest macOS version so the latest compatible version can be installed on the older version...
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