On Dec 30, 2009, at 1:05 AM, Noob Centos Admin
<centos.admin@xxxxxxxxx> wrote:
> Hi,
>
>> Try blocking the IPs on the router and see if that helps.
>
> Unfortunately the server's in a DC so the router is not under our
> control.
That sucks, oh well.
>> You can also run iostat and look at the disk usage which also
>> generates load.
>
> I did try iostat and its iowait% did coincide with top's report, which
> is basically in the low 1~2%.
>
> However, iostat reports much lower %user and $system compared to top
> running at the same time so I'm not quite sure if I can rely on its
> figures.
Yes, I'm not sure iostat's CPU numbers represent the full CPU
utilization, or only the CPU utilization for IO.
>> How many cores does your machine have? Load avg is calculated for a
>> single core, so a quad core would reach 100% utilization at a load of
>> 4, but high iowaits can generate an artificially high load avg as
>> well
>> (and why one sees greater than 100% utilization).
>
> It's a dual core that's why I was getting concerned since loads above
> 2.0 would imply the system's processing capacity was apparently maxed.
> However, load and percentages don't add up.
They never do because of the time scaled averages.
> For example, now I'm seeing
> top - 14:04:30 up 171 days, 7:14, 1 user, load average: 3.33,
> 3.97, 3.81
> Tasks: 246 total, 2 running, 236 sleeping, 0 stopped, 8 zombie
> Cpu(s): 13.3%us, 16.0%sy, 0.0%ni, 67.5%id, 3.0%wa, 0.0%hi,
> 0.2%si, 0.0%st
>
> iostat
> Linux 2.6.18-128.1.16.el5xen 12/30/2009
> avg-cpu: %user %nice %system %iowait %steal %idle
> 3.28 0.20 1.16 2.38 0.01 92.97
>
>
>> I really wish load would be broken down as CPU/memory/disk instead of
>> the ambiguous load avg, and show network read/write utilization in
>> ifconfig.
>
> Totally agreed. All the load number is doing is telling me something
> is using up resources somewhere but not a single clue otherwise!
> Confusing, frustrating and worrying at the same time :(
Maybe someone could write a command-line utility that outputs the
system load broken down into CPU/memory/disk/network. Call it
'sysload' and take the system configuration into account.
Take a look at your iptables setup, make sure the blocked ip rules are
checked first before any other and drop the packets without any icmp
(give em a black hole to stare at).
-Ross
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