Trying to post this question on here. I've posted it on the Ubuntu forums as well with no replies.

Recently I upgraded an HP ProLiant DL380 G4 server from Ubuntu 10.04 server to Ubuntu 12.04 server.

Upon doing so, the server will not - at random times - get to a load of 400+ and then become completely non-responsive. I use an SNMP graphing program (cacti) and the load steadily increases by about 10 every five minutes until it gets over 400 and the graphing stops.

The graphs may not be accurate, but the CPU load averages about 3% before this happens - and right when the load starts increasing, it jumps to about 25% for 15 minutes and dramatically dips down to less than 1% (about 0.3%) until the graphing stops.

I'm not able to open a SSH tunnel to the server to do anything. I've checked the /var/log/syslog and all logging stops at that time as well - with nothing else in there.

The odd thing is - the server still responds to DNS queries for the zones it is authoritative on during this time - and at normal speed.

Just not sure what the next step would be in order to find out what is going on - and how this issue can be corrected. The server cannot stay with Ubuntu 10.04 Server and needs to stay upgraded.