OSDev.org

In a preview build, Windows now let you mount EXT4 partitions.

https://www.bleepingcomputer.com/news/m ... -in-wsl-2/

First do you think this will become standard (in production Windows) in Windows in the future?

If it becomes standard, will it not kill exFAT? I'm making an assumption that the Windows EXT4 filesystem can also mount EXT2 partitions. That means that small companies that want to have filesystem interoperability will likely choose EXT2 because it is relatively simple and unlike exFAT completely free to implement.

Because of this I'm unsure Microsoft will do actually do this.

Short answer. No.

Longer answer, exFAT is the standard filesystem SDXC cards larger than 32GB, so many consumer devices already talk exFAT to use such SDXC cards.

It is these devices that will keep exFAT alive.

You missed out the important part of the announcement. This build lets you mount ext4 partitions in WSL.

The only way I could really see the recent addition of ext4 mounting to WSL causing mobile devices to standardize on ext4 (actually, probably ext2) rather than exFAT is if WSL itself is an indication that Microsoft is planning on having Windows transition to using Linux instead of NT for its kernel. I wouldn't place high odds on this, but it's not completely farfetched either. The industry has standardized on *nix over the years, and NT is the last man standing of kernels with significant market penetration that aren't some kind of *nix. And it isn't even that all the old vendors of non-Unix kernels have died and taken their kernels to the grave with them. Some very significant vendors transitioned their operating system from their own kernel to a Unix one: Apple acquired NeXT (bringing back Steve Jobs in the process) and built on NeXTSTEP to rekernel MacOS to use Mach, Novell acquired SUSE, wrote compatibility layers going either way between Netware and Linux, released a new server middleware product that could operate either on top of the Netware kernel or on Linux as part of a distribution spun of from SUSE Enterprise Server, and then killed support for the Netware kernel in their next release of the middleware product.

So it's not out of the question that Microsoft could decide that NT no longer serves their interests and that they want to rekernel Windows to use Linux, and the odds that it's technically feasible are good too, as the Win32 API was built to be kernel-independent from the start, too (it ran on both NT and the cluster of vaguely kernel-ish abominations that was the DOS/Win16 core of Win9x, and has since been independently implemented by Wine).

***If*** MS goes that route, then ext4 will likely become the main filesystem for Windows, and in that case Android, which already uses the Linux kernel, is likely to start defaulting to at least ext2 (maybe ext4) for SD cards, and then everyone else will follow.

But don't hold your breath. At the moment, Linux instances running in WSL can mount ext4 partitions, but, to my knowledge, that functionality is not available to windows programs.

If you see MS start making significant contributions to Wine, and especially if you see it buy a company that puts out a Linux distribution (for example, Canonical), **then** it will be time to get excited.

I'm not sure where the EXT4 support lies. Is it completely in the Linux subsystem or is it a standard Windows filesystem? Would it be possible to migrate the EXT4 support out of WSL so that it is system wide available? Any licensing problems?

You can access files in the WSL filesystem from Windows, so I guess in that sense it is system wide. But I would expect a performance hit and, as far as I can tell, the mounting/unmounting has to be done from WSL.

I can't see any reason why Microsoft would replace NTFS with ext4 as the native filesystem of Windows.

Exactly. Microsoft. doing away with NTFS? That'll never happen, and I could list many reasons why.

They're already on it. ReFS supposed to be the successor to NTFS. However I'm not sure how widespread its usage is these days (I'm a UNIX guy).

This is interesting though, and questions how good the VFS in WinNT actually is (and confirms that NTFS is not going to be replaced in the foreseeable future).
Cheers,
bzt

ReFS can't be used on boot volumes and can't host a paging file. Also, it doesn't support disk quotas, EFS, extended attributes and a few other features that are useful for a general purpose file system. It's only had limited take-up in server situations (the only application it is supported for) , but would be totally unsuitable for general purpose Windows usage.

NTFS is here to stay for a little while. ReFS may eventually become widespread. But it is intended for servers, and I have never heard of it before, and am very familliar with Windows.

No, EXT4 would be the replacement of FAT and exFAT for portable devices, this was the original question. NTFS is not in question here. EXT2 would benefit companies who don't want the extra hazzle with paying royalties to Microsoft. Basically, I can't see it happen as Microsoft want to milk companies for exFAT royalties.