OS : Centos 6.[3|4|5]

Setup : An NFS mounted volume which has a deep directory structure with lots of little files. NFS share lives on a NAS.
by deep, i mean many little directories and sub-directories with lots of little files.

Problem : If I want to find the disk space used by this directory, I run the du -shc command, which takes ages !

Is there a quicker way to do it ? I don't mind if the end result is a bit off by 5 to 10 %
I could run the find command, but that takes ages too. Looking for something which is as quick as df.

This directory sits with other files and directories, or i would have used the df command.

Appreciate your time.

I found du is faster than ls -lR | <script to sum up data> - find will be even slower than ls. Probably a multithreaded version will go faster (so du -shc parallel in all subdirs).
From the other hand you can try to run it from crontab, store the result - and you will always have an approximate result.