Build massive number of assetbundle very very slow

For some reason, I need to pack my resources into small size of assetbundles, so there's about 5000+ assetbundles in my project. When I build them by using "BuildPipeline.BuildAssetBundles(string outputPath, AssetBundleBuild[] builds, BuildAssetBundleOptions assetBundleOptions, BuildTarget targetPlatform)", it goes very fast at first, but become extremely slow after built about 1000+ assetbundles. It will take ~1 sec to build one then; and it takes ~5 secs when finished about 2000 abs.
For building 5000+ abs, it totally takes about 12 hours. Files total size is about 400MB uncompressed.
It it the I/O problem or it's an issue of UnityEditor? Or just my own problem?

 

It happens for just about any Unity automated process.. I am guessing this has to do with some undo stuff or memory stuff. Only hope is to separate build process into more manageable chunks..

 

Thanks for your reply! Guess I need to change many things to avoid that many assetbundles……

 

I have the same problem. I have 15K assetbundles and it takes more than 20 hours!!!!