What can I use to help me gauge when the server is getting overloaded with users.
At present I run the server mainly as a proxy server with about 100 users. The bandwidth at the data centre is 100Mbps connection with total bandwidth used last month = 17431.16 MB

I would like to add a VPN in future but feel that this might overload the bandwidth as instead of it just being web traffic it will the entire client TCP connections.

I would like to monitor this before it gets to the stage where users are complaining but not sure how to gauge whether the proxy is being overloaded. It is used mainly for video traffic.

.....

Do monitoring and graphing using snmp and rrdtool and you will be able to pickup when your link gets saturated.

It's not so much the bandwidth that I am worried about but also the server cpu and memory though I don't think that is an issue so far.

Is it this one?
http://dag.wieers.com/rpm/packages/perl-Net-SNMP/

DO I have to allow snmp in the firewall?
http://www.schemathings.com/?p=11

You do not have to allow snmp through the firewall, everything happens on the local host. with snmp and mrtg you will be able to monitor the cpu and memory usage as well.

take a look at these likes for more info on setup

http://www.linuxhomenetworking.com/w...er_Performance
http://www.linuxhomenetworking.com/w...MRTG_for_Linux

Does this look like rrdtool.
I wondered if my host already had installed a monitor as rrdtool was already on the server.

http://img404.imageshack.us/img404/6500/mem.gif
http://img691.imageshack.us/img691/7264/trafficj.gif
http://img218.imageshack.us/img218/6468/cpu.gif

Yes that's it.

Does the traffic look saturated from those graphs or any problems with the server?
I know sometimes when I use the proxy myself it works perfectly for streaming video but it sometimes takes a while for the pages to load even with caching.

No u still have lots of capacity

But what are you looking at to say that, the bandwidth?
What could be causing a slow load of some pages on the squid server then?
100Mbps = 12,500 kbps?

The issues could be upstream from those graphs your system is not over loaded at all.

If my data connection is 100Mbps, what would be saturation on those graphs?
The stats show 300kbps max per month.
I sometimes log inot the server and regularly see iptraf in the 4,000 kbits per sec, every now and then 10,000 kbits per sec on eth0

I sometimes log inot the server and regularly see iptraf in the 4,000 kbits per sec, every now and then 10,000 kbits per sec on eth0
Doesn't seem to match up with the rrdtool stats