All the NFS file systems are under monitoring?
Yes, all the disks or partitions with appropriate permissions will be monitored. You can navigate to the OOTB dashboard and Click on the Hosts > Double Click on any Host > In this refer the Disks Dashlet.
How to find the files which is of big size?
forfiles /P D:\ /M *.* /S /D +"01/17/2012" /C "cmd /c if @fsize gtr 209715200 echo @path @fsize @fdate @ftime"
Linux: It lists all files that has size bigger than 1G
find / -xdev -type f -size +1000M