Thanks Guys i've checked the disk space and it looks fine.
I investigated further and the checks were happening, just very very slowly, when two hosts went down it appeared to get stuck on them.
/usr/local/nagios/libexec/check_ping -H 10.32.44.48 -w 3000.0,80% -c 5000.0,100% -p 15 -t 20
I think it was where it was checking a host using the check-host-alive command It was taking ages, so I changed it to this.
'check-host-alive' command definition
command_line $USER1$/check_ping -H $HOSTADDRESS$ -w 3000.0,80% -c 5000.0,100% -p 5
Now it only ping 5 times rather than 15, so its not waiting for 15 icmp packets, this worked fine on the old config but on here didnt.
Its running okay now, but not sure if this is what fixed it or not. Its completing all 313 checks in 5 minutes or less which is good, before it wasnt even doing half that in an hour!
Could someone post their checkcomands.cfg file for me to have a look at check_ping
and check_host_alive directives to see what you have used for them?
It think this might be where the problem lies.