EPiServer 8 uses the blob storage, and appData basePath tells the EPiServer where to save those blobs / files, as well as search index.
@Dejan, Thanks for your feedback,but I find there are folders named "modules" and "ModulesRepository",I think after upgrade 8,this package should be moved into "modules/_protected" folder.so at least to keep clean the folder.
ModulesRepository still may be used if you have enabled AddOn installation from UI.
Check this article: http://world.episerver.com/blogs/Khurram-Hanif/Dates/2014/3/EPiServer-76-Protected-Site-Add-Ons-location
You can run a command in package manager console in order to move modules.
Thank you,Dejan.I've read through the link you recomended.
I think after upgrade epi to 8,we needn't vpp settings,right?can we remove