maximum number of terabytes catalina can boot from on a 2012 Macbook Pro 15" retina external hd

What is the maximum number of terabytes catalina can boot from on a 2012 Macbook Pro 15" retina external hd?


Older OSX versions could not boot from more than 2TB.

MacBook Air 13″, macOS 10.13

Posted on Oct 10, 2023 9:00 AM

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Question marked as Best answer

The drive size limits were expanded by doubling the width of the field that contain the allocation block number to 32 bits wide when HFS+ was introduced, and made the way forward with Intel Macs, around 2004.


Drive sizes limited to 2.2 Terabytes is a hold-over from a previous era, was annoying, and has been pushed so far back we can't even see that limit any more.


That means that since 2004, the maximum Volume size has been 8 ExaBytes, which I believe is 8 Thousand Million Terabytes. That same maximum size was retained for Apple File system, APFS.


The limits are so large, you can not possibly buy a drive that exceeds them.

Posted on Oct 10, 2023 1:11 PM

1 reply
6 replies

Oct 10, 2023 12:32 PM in response to Grant Bennet-Alder

starting in 2019, i think, Macbook Pro could come with 8TB internal which would have to be the boot volume when purchased.


I am currently running Catalina on 2012 Macbook Pro 15" retina external hd.


What is the maximum number of terabytes catalina can boot from on a 2012 Macbook Pro 15" retina external hd? Is it 2TB or up to 8TB?

Question marked as Best answer

Oct 10, 2023 1:11 PM in response to dgd

The drive size limits were expanded by doubling the width of the field that contain the allocation block number to 32 bits wide when HFS+ was introduced, and made the way forward with Intel Macs, around 2004.


Drive sizes limited to 2.2 Terabytes is a hold-over from a previous era, was annoying, and has been pushed so far back we can't even see that limit any more.


That means that since 2004, the maximum Volume size has been 8 ExaBytes, which I believe is 8 Thousand Million Terabytes. That same maximum size was retained for Apple File system, APFS.


The limits are so large, you can not possibly buy a drive that exceeds them.

maximum number of terabytes catalina can boot from on a 2012 Macbook Pro 15" retina external hd

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