Is their any issues for storing large data files in a database instead on server??? what big sites actually do like box.net etc :S
I don't know specifically how those sites store those files but my guess would be the files themselves are stored on a server and the location of those files is stored in a database. In a simple world think of it this way: the database has columns for video title, video ID, and video location and data may be 'Never Gonna Give You Up', 5328, 'http://www.youtube.com/video/a2b73f89'. The advantage is that the database is smaller, quicker to query and doesn't have to serve up tons of files itself. When a user wants that video it goes to the database finds its location and sends that information to the browser so the browser can go find it.
thnx but how gmail works if i download a file from gmail and connection is broken or i signs out the download link works no more.. is that means files are on db or somewhere else?
Sites are like box.net, dropbox, etc. are online storage sites. You can store your personal files there and share with friends. Sites like Youtube are for video files. You can upload your video for others to see. Sites like Gmail are for sending / receiving emails. You can send files using attachments. All these sites are owned by big companies. They have huge servers all around the world.
Think of a library. The shelves are the storage area and the card catalog is the database. The card catalog doesn't hold books, it holds the specific locations of the books in the storage area. Granted technology is moving fast, but bandwidth, transfer speed, file size and processor speed are still issues so that is why the two are still seperate and we don't just merge it all together. Right now it is still faster for you to look up a book on a card catalog, walk over to the shelves and retrieve it than it is for a computer to hold and serve that data. The same thing applies to sites holding and serving enormous amounts of enormous files.
Databases are programs that run on servers, everything runs on Servers, servers are basically computers with a specific usage