Min. Free Space and Defrag?

[DiggsNC]

So I did some searches and checked the wiki here http://lime-technology.com/wiki/index.php/Un-Official_UnRAID_Manual#Min._Free_Space and didn't find my answer. I recently filled up my Unraid server V4.7, and while reading through the threads here noticed someone mentioned Minimum Free Space settings. So I looked into this having about 600GB of free space across 5  2TB data drives, but unable to move files to the server.

 

So my question is, Can I change this setting now or am I stuck with where I set it originally?

 

Also, is there a "Defrag" type utility for linux/unraid, and is it something I should even be concerned with? Yeah, I am a windows guy.

 

Lastly, I read up on the split level info and understand how that works, so I know sometimes files may get moved / not moved based on those settings, but I think I am good on that. However, can that be changed? Not nearly as important as my first question about Min Free Space.

 

Thanks!