First, we highly recommend you to use Temporary storage. Because ASP.NET is built in such way that all client requests are kept in memory as one data thread.In many cases, this allows improved system performance and reduced time it takes to process each request.However, when you upload large files, your application and system performance will go down proportionally to file size. This is because more memory and processor power is required to process these requests.
Also, FileUploadControl uses pattern:
1. Show Command Panel with command buttons
2. Upload several files in several post to temporary storage
3. Commit changes from server temporary storage to real storage (Save to persistent storage, like SQL, File or external WebService).
So, If you turn off temp file storage you can not use FileUploadControl, but you can use McHtmlInputFile and show progress information (see lesson 0).
I wish, my information helps you.