file storage and data storage - developer questions

[Robert Mundkowsky]

So there seems to be a few different data storage systems that edx uses.

For small data you can use edx Fields which likely get stored in a database. I guess mysql on real edx.org or on edge.edx.org and SQLite if you are doing development on your own computer.

For large files, if the files are course content, there seems to be idea of Modulestores. I assume these are stored on S3 and some info in a database using either XMLModuleStore, DraftModuleStore, or Split Mongo .

For large files, if the files are not course content, for example student recorded audio files, then I guess developers can store then on AWS S3 or OpenStack Swift Object Store.

So I wonder:
1) Can you put some amount of data on ESB for processing (e.g. if you need to use tool that does not understand S3)?  If so, how much data? Per student?  Is it removed per student session?
2) How much data can you store in S3?  Or is S3 paid directly by course admin, hence they can use as much as then want to pay for?
3) How much data can you store in Fields?  Is admin charge for storage fees?
4) How much data can you store in Modulestores?  Is admin charge for storage fees?
5) Is there more info on using S3 or Swift?   All I found was following, granted maybe it has enough info:  https://openedx.atlassian.net/wiki/display/OpenOPS/Configuring+Data+Storage