How do you design global file storage and file sharing services like Google Drive, Dropbox etc?

How do you design global file storage and file sharing services like G

1.	How do you design global file storage and file sharing services like Google Drive, Dropbox etc?
Answer» What are some of the Required Features? Users should be ABLE to upload, DELETE, share and download files over the web. File updates should be synced across multiple devices. What are some of the COMMON problems encountered? Where to store the files? How can you handle updates? Should the files be re-uploaded or does just the modified version has to be updated? How to handle updation of two documents at the same time? Possible tips for consideration: Consider using chunking for SPLITTING files into multiple SECTIONS for supporting re-uploads of a particular section rather than the whole file. Make use of cloud storage for storing the files.