[ngw] Linux Web access issue

[John Dickey]

Having a problem lately on our Linux server that supports web access.  The issue is that users web access at times can not reply to emails.  Then after looking at the server df -h notice that /dev/xvda3  partition is at 100%.  I go in and clean up some of the logs to bring it down in the 70% range and users can reply again.  Today, the same thing but the usuage on /dev/xvda3 bounces around from 77% up to 97%. 

My question is what is causing this to happen and how can I get it to stop?

thanks in advance for every ones help!!