Volume Needs Repair

well i was trying out onyX and as you start it verifies the structure of the System Files in the Startup Volume. In that it showed me an error about my Disk. Thus i went to disk utility and verified it there and this was the error it gave me

Verifying volume “Macintosh HD”
Checking HFS Plus volume.
Checking Extents Overflow file.
Checking Catalog file.
Checking multi-linked files.
Checking Catalog hierarchy.
%)
Checking Extended Attributes file.
Checking volume bitmap.
Checking volume information.
Volume Header needs minor repair
The volume The volume sh HD needs to be repaired.

Error: The underlying task reported failure on exit


1 HFS volume checked
Volume needs repair

there are certain instructions given about the repairing though they aren't very clear as to what shall happen.

Will I lose my data? Is it normal for this kinda stuff to happen? I'm yet waiting and deciding about switching over to Leopard with all the problems i see people face. Would this be the right time to do that?

If you need to repair your startup disk, then you will need to boot from your OS X install DVD, and run disk utility from there. You just have to pop the disc in, hold down C, and then launch disk Utility from the install menu.

I don't think there's any major problem here...it says Volume Header needs minor repair...

So would i need to back up my data or something?

Check out this post about fixing errors using the fsck command. Using it skips the hassle of booting from the DVD. You shouldn't need to back up any data, though in a perfect world you would have, anyway.