the load you see in the panel is a measure of the computational work being performed by the system,
you'll see the same thing in the top right of the window if you run 'top' in a terminal.
although that shows 3 sets of numbers, over 1 minute, over 5 minutes, and over 15 minutes.
it looks like the enhance panel graph is showing the load over 5 minutes.
think of it as a percentage of capacity, with the value 1 being 100%
at 0.2, it's at 20% of capacity, at 0.5 it's at 50%. for a single (v)cpu.
at 1, it's at 100%, it's doing as much as it possibly can, and more processes are waiting for cpu time..
it's not necessarily bad, you'll see some slowness, but performance may still be perfectly acceptable.
the higher above 1 goes, the more slowness you'll see, and it'll become increasingly noticeable.
also, that figure of 1, is for a single cpu. if you have more cpu's, add 1 integer to the load capacity for each cpu.
a 4 cpu system can have a load up to 4 without experiencing any drag on performance.
a 4 cpu system with a load of 1 is only at 25% capacity, it may be a single cpu running 100%, it may be each cpu running at 25%.
think of it as a road, with cars as each process, at a load of .25, 3 quarters of the road is empty, you can easily fit more cars without problems, at a load of 1, it's completely full, and any extra cars have to wait to use the road.
for a 4 lane highway, a load of 1 is the same amount of processes (cars) as the single lane road, but you have much more capacity free still. at a load of 4, the highway is now completely full and extra cars have to start waiting again.
now comes the time intervals..
again, assuming for now, a single cpu system, a load of 1.05 will show some slowness, if it's just a spike over a short period, it may just be a mild irritation, nothing major, but over 15 minutes or more, it starts become a very noticeable problem.
basically you want the load to be a small number, but not too small. if it's always 0.05 - 0.1, you could consider the system overpowered, you're paying for resources that are never getting used.
if it's always around 1 or higher, then the system is underpowered, you need more computing power.
a range of .2 to .5 utilisation (per cpu) is good for a shared webserver, not too low that you're wasting lots of money, but leaving plenty of capacity free to cope with traffic spikes.
