Guys any one has idea about the CommVault systems 7 hours coding round.it was completly about virtual file system implementation.

I have cleared the first 2 rounds of CommonVault systems interview process.Next round is a 7 hours coding round which is completly about virtual file system implementation.
I am a newbie to that topic.I still have 1 week of time.
Any one please tell me how can I prepare if possible share some useful links.
Thanks in advance.