How does Additional Layer Storage (ALS) work?

[lyj199907]

Recently, I've been working on improving theNyDus-Storage-plugin ，which provides support for podman to use nydus format images with the feature of additional layer store(ALS).

But, after read the following issues and blogs, I still can't understand how it works

https://medium.com/@mohit2501tyagi/lets-walk-through-podman-37636cf223c5
containers/image#1109
containers/storage#795

so could the community provide some notes or blogs about the working principle of the additional layer store ?

thanks a lot !!

[lyj199907]

@ktock Can I get your help with this?

thanks a lot!!!