[CentOS] High system load but low cpu usage

[Steven Tardy]

On 06/08/11 02:26, Emmanuel Noobadmin wrote:
> Cpu(s):  4.1%us,  2.5%sy,  0.0%ni, 76.4%id, 17.0%wa,  0.0%hi,  0.1%si,  0.0%st

> 02:50:01 PM     all      2.17      0.00      2.18      4.30      0.00     91.35
> 03:00:01 PM     all      2.47      0.00      2.23      3.57      0.00     91.73

top Cpu(s) line is averaged for all cpus/cores. to display individual cpus/cores press:
    1
you'll likely see one cpu/core being pegged with iowait.
to identify the offending process within top press:
    fj<enter>
to display the P column(last used CPU).
watch top for a few minutes to see what is using all of the disk io.

sar output is averaged over the 10 minute interval.
for smaller sar time slices edit cron file: /etc/cron.d/sysstat

disks are often swamped by "two things happening at once"...
   backups
   migrating a VM
   database upgrades
   .rrd average updates

-- 
Steven Tardy
Systems Analyst
Information Technology Infrastructure
Information Technology Services
Mississippi State University
sjt5 at its.msstate.edu