I had Snow Leopard install more than a month and today i have a chance to play around with the fire wall, i ran into an application call "DDServiced" is anybody know this is ?. Should i allow or block this app ?.

DDServiced is the Drobo Dashboard background daemon. I'm not entirely sure why it'd be asking for a hole in the firewall, unless it's for outbound connections when checking for updates... Are you updated to the latest version (1.6.1)?

Update: Apparently there are issues with the latest 1.6.1 with DDServiced using more system resources than necessary. I've seen CPU-hogging on my 10.6 machine.