Software update suddenly calling for twice the total space it initially said it needed

user1813 wrote:

I tried to install the Sequoia update on my 2020 MacBook Pro. It said it needed something like 19.7 GB, but I left 23 GB for extra space/just in case. While downloading, it said it was using even less space, I think around 17 GB.

It finally finished after several hours, but now there's an "Install macOS Sequoia" application open, and it says it needs an additional 28 GB on my disk, after the application took up a whole lot of storage already.

My Mac didn't give me any warning that a huge other chunk of space would be needed. Is this correct, or did I somehow install it wrong, like maybe it's downloading a copy of something twice/multiple times, or not counting some space? Also, is most of that space only temporarily reserved for installation, and I would get it back afterwards, or is it all just added onto the system?

I don't think it will even function properly for my basic school files and programs to edit documents if the system size is so big. Maybe I'm wrong, but it seems weird that a software update would be so large. Certainly never had the same issues with updating my iPhone.

SSD like to have 15-20% free storage at all times. If you do not have that, it is time to do some house cleaning.

How to free up storage space on your Mac - Apple Support

Free up storage space on Mac - Apple Support

The installer needs to expand and extract the files it needs to install the system which takes up additional space other than the installer size.

It's generally recommended to keep a minimum of 80-100 GB of free space on the boot drive to optimize system and application performance.

With as little as 23 GB of free space it could get filled up quickly thus preventing you from booting up and running. We've seen it happen here. If you need an external SSD to house Photos libraries, music libraries or iMovie libraries this portable SSD from OWC (MacSales.com) is easy to carry and use: OWC Envoy Pro MINI.

Just some food for thought.

user1813 wrote:

Will do, but will I get to free up any of the total 48 GB (on top of the space my existing system uses) this is asking for after I update? Just seems like a lot on top, especially since currently my system only takes up 13 GB.

Once the macOS installer has upgraded macOS, then most of the storage used for the installation process will be cleared so you have access to it again. macOS will even delete the downloaded installer once macOS has been successfully upgraded.

Keep in mind though that even during the macOS upgrade process where it requires up to 50GB, you should still have at least 20GB+ of Free storage space anyway.....so that would mean before the upgrade process you should have 70+GB of Free storage space. If you don't have enough storage space, then you don't have enough storage space for your usage anyway irregardless that this only happens during a macOS update/upgrade.

Also, the only places where you actually see the Free storage space value listed is within Disk Utility or the Apple System Profiler. Everywhere else macOS is showing the "Available" storage space which is very misleading and should be completely ignored since the Free space value is the only one telling exactly how much storage you have that can be accessed immediately.