Forgetful Dreams

I had a dream recently, and I remember it so clearly, every single details from places and whom I'm with. I shared it to my friend that he is in my dreams. Then, he asked me, how many GB your brain memory has? Because, he said when he had a dream he always forget it all when he wakes up.

I really don't know if he people have different memory brain capacity, which I do believe we all have  the same. Though, there are people whom they called have a photographic memory. Not so often I remember my dreams, I have only few. Sometimes I just remember it partly. But most, I forget it all too when I woke up, and no matter how I tried to remember it, I really can't. Though, I only want to remember those happy dreams I know I have, those bad one... better not too :)