The new Windows 10 build is available to participants of the Windows Insider program, who have opted for the Fast ring—this is the branch that receives test builds earlier in the development cycle than those that get pushed out to the Slow ring. As a result, they can be more buggy and "might be more painful for some."
WSL 2 leverages Hyper-V features to operate in a virtual machine. With the previous WSL 1 implementation, Microsoft instructed users to place their Linux files on their C: drives. But for WSL 2, those files must now be placed in the Linux root file system, a change that enables better performance when accessing files.
"This new architecture, which uses a real Linux kernel, changes how these Linux binaries interact with Windows and your computer’s hardware, but still provides the same user experience as in WSL 1 (the current widely available version). WSL 2 delivers a much faster file system performance and full system call compatibility, which lets you run more applications like Docker!," Microsoft explains.
The "lightweight utility VM" launches at startup and chews up a small amount of memory, but Microsoft says it is only a small proportion of the user's total system memory, giving in an overall "small memory footprint." There a drawback with how WSL 2 is implemented, however. Microsoft notes that users will see slower file speeds compared to WSL 1 when accessing Windows files from a Linux application, and vice versa.
Outside of the improved Linux implementation, the latest test build contains a few other features and changes. Some of the notable ones include...
- New download throttling options for Delivery Optimization
- Data table reading improvements to Narrator
- Windows Ink Workspace takes up less screen real estate
There is also the usual round of bug fixes, including one that was causing some users to see a 0x8007000E error code while the downloading the build due to high RAM consumption.
i think it really will be mostly like a service pack for 19H1. and rumor is if there are any new features they might be turned off by default
— Mary Jo Foley (@maryjofoley) June 5, 2019
As for the test build with WSL 2, it will arrive in polished form in the first half of next year.