When using columns size on disk is showing the exact same value as size, for folders and files.
In this example you can see from the file properties that the size on disk should only show 356 MB but the selected file just shows 846.
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It's unusual for Size on Disk to be smaller than Size.
Is that a sparse file? (Those are unusual in themselves.)
Which filesystem is the drive using?
It's an NTFS drive, and it's not just those files, but lots of files I have that are smaller on disk than their reported size.
They're smaller because I've used the windows 10 "compact" application to compress them. But it's not the same as standard NTFS compression.
The MS documentation site is actually a bit sparse on it so the best resource I've found about it is this site (and I did use the CompactGUI to shrink them). ImminentFate/CompactGUI: Visual Interface for the Windows 10 Compact Function (github.com)
Just to provide you with a bigger picture view
You can see here that I've saved ~60gb on my steam library by using compact. (screenshot was taken with WizTree)
Details
Here: https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/compact
And here: https://social.microsoft.com/Forums/en-US/491760f7-c084-4295-823c-64a44c24253b/differences-in-ntfs-compression-between-the-windows-explorer-and-compact-based-on-new?forum=win10itprogeneral
I hadn't seen that second post, but the official microsoft documentation doesn't actually include info on the command used to do it (because all of mine is in XPRESS16)
You literally get more info by going to CMD and typing compact /?
Bottom line - they are sparse files, as noted in the second link.
In the next update, we'll add Preferences / Miscellaneous / Advanced: [Filesystem] size_on_disk_thorough which you can turn on to report the compressed sizes of these files.
However, it will be off by default, and we recommend against turning it on unless you really need it. Turning it on will make folder size calculation significantly slower.
This is really a bug in Windows. Unlike the standard NTFS compression modes, Windows reports files compressed with these esoteric/hidden NTFS compression modes as "uncompressed", and there is no fast way to find out if a file has been compressed with these modes.
All we can do is ask for every single file's size on disk, on the off chance that the file has been compressed. That's what the new mode does, but the extra per-file query is very slow (compared to the speed of reading the main directory listing and size details). It's extremely slow over network drives, and the information is not cached by the OS when re-reading a folder, either.
So we don't recommend turning this on, unless you really need to know for some reason.
(Given how half-baked support for those command-line-only compression modes is in Windows, I'm not sure that using them at all is a good idea, to be honest, but that's up to you.)
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Is there any reason why Directory Opus can't use whatever method WizTree or TreeSize uses to calculate file/folder sizes?
Wiztree can give me a full tree browsable by size in less than 3 seconds for a 1tb SSD (Including both size and size allocated)
I'm not trying to be overly difficult, I'm just not sure how other applications are able to perform the calculation so efficiently.
See how fast it is when it arrives. It may not be that much slower on an SSD.
Beyond that, I have no idea how either of those programs works. If there's technical information about them somewhere, we can look at it.
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According to the Wiztree website, when scanning full drives it reads the MFT directly and builds it's size tree out from there. I'm not sure how it handles individual folders when you scan them though.
Thanks for adding in the new setting though, and hopefully it's not terribly slow. I love Directory Opus and really appreciate how responsive you are to customer concerns! Keep up the good work!
Sounds similar to Everything. There are some reasons we couldn't use that method all the time, but it is interesting as an option.