The cache you configure on source doesn't matter. Set it to 5GB because it is not used. At source we only create digest files.
Take a look into our Best Practice Bookhttps://veeampdf.s3.amazonaws.com/guide ... vmware.pdf
2% of source data = digest size (2% of 1,5TB = 30GB)
+ 10GB temp space
+ 5GB for the not used blob-file.
= 45GB diskspace but only 5GB cache configured
No of OSs * 10GB = space for one side
+ 20GB temp space
+ 1x cachesize for prepopulated cache.
2 OSs (Windows 2008 and 2012) * 10GB * 5 (sides) + 20GB (Tempsize) + 2 OSs (Windows 2008 and 2012) * 10GB = 140GByte
In this example you configure your target cache to 20GB