suspicious act in my server

[nlimbu healthnet org np]

Hi all!

My mailserver seems to be accessing harddisk all the time. I didn't face such 
situtation of continously accessing harddisk in previous times. 

Using ps command, I found only normal process. Using top command, I found 
sendmail running at the top but not consuming much memory (less than 1%). When 
using netstat -a, I found lots of connection of sendmail and domain.

What process might be using my harddisk for such a long time (nearly whole day)? Is 
somebody trying to access my server or some program is acting abnormally?

Hoping for your help

With Regards
Nabin Limbu
HealthNet Nepal
Ph : 977-1-429722