Yes, it is possible to use the HTML 5 File API with the Amazon S3 multi-part upload feature. You would need a server backup as well as Amazon API keys.
Amazon S3, a web service offered by Amazon Web Services provides storage through web services interfaces. Amazon launched S3 in 2007.
Create multipart upload with Amazon API and send "key"(filename) and "upload id" back to the web page. For the multi-part, you need to send part data directly to Amazon S3 via the "part upload URL" using "date" and "auth header".