Guys problem with my hard drive in the serverrrrrrrrrrr

Hi guys
When i check the Service Status i find that Disk hda3 (/) DMA+ is 93% , i dont know why ,but my clints only using 7 GB , and my hard is 80 GB .
Is there a way to know the biggest folder or file in the server , and how can i solve this.
thanks

 

 

 

 

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