Help with btrfs project

[Sudip Mukherjee]

On Wed, Aug 20, 2014 at 8:03 AM, Nick Krause <xerofoify at gmail.com> wrote:
> Hey Guys,
> This commit seems to be needed to fixed up based on what the btrfs
> developers, are stating on their wiki.
> Other then the TODO list, which we can discuss here,  is there any
> other parts of this patch that need to
> be rewritten, it's merged as of now but I can recreate  new patches if
> needed from Linus's tree. The project
> idea is Clear unallocated space on the btrfs wiki. I AM NOT asking you
> to write the code just want  to known
> is how you want this cleaned up.
> Cheers Nick
>

Hey Nick,
It seems like you are an expert on btrfs . Can you please let me know
a few questions i have :
1) is btrfs better than ext4 ? if yes , how ?
2) what is the main difference in the implementation of ext4 and btrfs ?
3) I know very little about file systems , but i know ext4 uses
journaling file system. will you please care to explain what is
journaling file system?
4) btrfs supports online defragmentation ... how that is implemented ?

Thanks
Sudip

PS : a simple google search will give the answers  , but i will want
the answers from Nick .