With repair I'm going to loose my data?
Do I need to backup my data first?
Looks like you found the answer! No - a repair doesn't require you to backup data. It's a relatively safe operation.
On the other hand, it's wise to have a current backup before doing any action such as this. In fact (as I found out yesterday when my hard drive died) it's advisable to always have a recent backup of your data (and yes, I did have one!).