Upgrading from El Capitan to Mojave - 25GB disappeared.

[krs]

I wonder if this DirEqual.app could help a bit more...???

DirEqual - quickly compare Mac folders.




- Patrick
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I tried running that last night.
This app I think is good to compare maybe a folder, but not two 500GB drives - it seems to go through the data bit by bit, just takes forever and with me it never finished.

And, say Mojave uses a better compression algorithem than El Capitan for some files, I assume DirEqual would flag that as being different even though in practice the data is still retained properly.
I think the app is great to check and validate a back-up but not to compare the data after migrating to a new macOS.

On the weekend, I'll try to find some time to compare the Mail message and folder counts between Mojave and El Capitan - if those are not wildly different I'll just forget about the discrepancies.
Just strange that I couldn't find anything related to this on google - people are always asking "Where did my hard drive space go?", not "Where did 25GB of free hard drive space come from?"

 

[MacInWin]

Give DaisyDisk a try. Nice graphical display to help you find big hitters.

 

[krs]

I haven't done any more investigation on this 25GB disappearing, but based on the recent threads, discussions and articles on the pros and cons of HFS+ and APFS, I think the 25GB disappearing might be perfectly normal since APFS is more efficient in the way it stores and handles some data.
25GB sounded a lot to me initially, but it's only about 5 1/2% of the 450GB total space used.

 

[Randy B. Singer]

I haven't done any more investigation on this 25GB disappearing, but based on the recent threads, discussions and articles on the pros and cons of HFS+ and APFS, I think the 25GB disappearing might be perfectly normal since APFS is more efficient in the way it stores and handles some data.
25GB sounded a lot to me initially, but it's only about 5 1/2% of the 450GB total space used.

Actually, if you go back to post #17, where you show the results of using Disk Inventory X...you say that it wasn't much help, but if you look at the results, there is something that jumps right out.

Just about everything on the chart on the left, over a certain size, is a tiny bit smaller in the chart on the right. Now, if you don't see any apps or documents that are missing, and your Mac is running just fine, that would seem to indicate to me that, indeed, APFS is a bit more efficient in how it stores things.

And when I think about it, it makes perfect sense. HFS+ was optimized for RDHD's. And so it left room on the physical platter between things for them to grow as you added new data to them, so they would still be contiguous for optimal read performance.

But APFS is optimized for SSD's. SSD's don't need to leave any room between things, as they don't read things based on physical heads moving to different places on a platter. Nothing needs to be contiguous because an SSD can access bits of data strewn across a bunch of registers all at the same time. So there is a lot less wasted space.