How much an adult should sleep?

How many hours an adult should sleep? Doctors/ Physicians recommend 8 hours for a healthy body. But what should be according to you? Because sometimes you have to ignore health and focus on hard work. I am a college student and I sleep around 10 hours daily and still feel tired. This should not happen. I live in a joint family and when I look at the routine of my Father, Uncle, or Elder brother who do business or a job usually sleep for only 6 hours and remain active throughout the day. So what's your opinion?