Why does Windows create $Extend\RmMetadata files on removable drives?

When did this start?
AFAIK it is recent, or has only recently become a problem requiring the installation of apps to facilitate safe removal of external drives.

This started with NTFS, a journalling filesystem that creates metadata continuously to help maintain data integrity. It's more complex than that but that's the basic reason for why/when it started.

Earlier filesystems - still used - like FAT and FAT32 don't create the same metadata files so there's a greater risk of data loss if, for example, you just remove an external drive without safely ejecting it.

As flash drives in particular have grown in capacity and are used to store larger and larger files like videos, so they have gradually changed from being formatted by default as FAT/FAT32. This may be why you haven't previously noticed that smaller capacity flash drives tended not to use NTFS.

Hope this helps...

I found this comment in Answers.Microsoft.com:-
The file C:\$Extend\$RmMetadata is an old Windows system file. Windows doesn't use this but it's not safe to delete since some of your applications still using it.

These files cannot be seen in File Explorer even with amended View options, however they can be seen in WizTree.
As I said earlier, and in another thread, I first became aware of them a few weeks ago, so I am puzzled as to why I'd never had problems with them before that.

Hairy Scot said:

I found this comment in Answers.Microsoft.com:-
The file C:\$Extend\$RmMetadata is an old Windows system file. Windows doesn't use this but it's not safe to delete since some of your applications still using it.

These files cannot be seen in File Explorer even with amended View options, however they can be seen in WizTree.
As I said earlier, and in another thread, I first became aware of them a few weeks ago, so I am puzzled as to why I'd never had problems with them before that.

First off, C:\$Extend\$RmMetadata is a folder, not a file. For example:


Second, the folder is used by the OS, not by applications.

Third, that same comment went on to state:

I recommend not deleting it, but if you're not comfortable on it taking a large amount of space, you need to perform a clean install of Windows 10 to prevent problems. (My emphasis)

IMO you would not need to do a clean install of Windows 10. A likely reason for the large size of the metadata folder and its contents is a growing number of bad sectors that the OS was trying to deal with automatically and journalling its efforts as it mapped bad clusters and moved data from them to re-mapped good clusters. If so, a clean install of the OS would do absolutely nothing "to prevent problems" with a failing disk.

I don't think I can add any further useful information so... hope this helps...