High load without explanation
Solution 1:
So load average is actually quite complicated, but my understanding that it basically is what is waiting in the run queue. So my guess is that you may have things waiting on IO. Here is a nice stolen snippet to see what is waiting:
ps -eo stat,pid,user,command | egrep "^STAT|^D|^R"
D : Uninterruptible sleep (usually IO)
R : Running or runnable (on run queue)
As pointed out, iostat works well as well to see if it likely disk.