push data to client/ keep checking the server side for any update to load

hi..

Im developing a web application to be used over the internet (not entranet) that means I have unknown of users accessing my web site.

I need to keep checking the server side every 30sec by creating hidden iframe to keep submiting to the server and check for specific updates( such database table). I think this way will reduce the performance of the server and not accepted!

is it true as I think? there is any other technique to this? is there some AJAX control to use instead?

note: Im fetching a small amount of text from the server

It really depends on your system and the expected number of users. Of course, every time you poll the server it takes some performance but in many cases the rewards outweight the performance hit.There are a lot of sites that do this and its not a huge performance hit if you are just retrieving a small amount of text. I would say go for it if you have the capacity.

Take a look at this: http://encosia.com/index.php/2007/07/25/display-data-updates-in-real-time-with-ajax/

The page method call for polling keeps the traffic level very low, compared to other techniques.