I just learned the lesson that for cron.daily tasks should be disabled for Linux servers.
I were having the headache that in some certain hour of each day, my servers run into high load average. I suspected that it is my app server’s problems, and I spent tons of time on optimizing my service servers. Optimization helped a little but high system load average was still coming. I wondered why. And l installed iotop by “yum install iotop” the day before yesterday, and found that “prelink” and “updatedb” did a lot of IO reading and writing. And finally I got to know that they were the cron.daily tasks, which is located under /etc/cron.daily/ .
So disabling tasks under /etc/cron.daily/, like mlocate.cron (will invoke udpatedb), makewhatis, prelink and others, will help your servers perform a lot better.
By the way, your should also edit /etc/crontab to reschedule the time for those daily jobs. The default hour is 4 a.m. in the morning. But your servers’ timezone setting might be different or your servers’ peak traffic might be at that hour, so modifying it to your servers’ valley hour will help performance.
After these modifications, WeBuzz.IM web IM services servers will run a lot better from now on.