[mrtg] Re: server ports

[Alex van den Bogaerdt]

On Fri, Jul 04, 2003 at 05:26:37PM +0200, Alberto Moreno wrote:
> I am monitoring ethernet network with 100 mbit bandwidth.
> The ports, where the servers are connected,  use 300 or 400 kbs except
> when I make server backup , then the ports use 40 or 50 Mb. Is this
> normal???  should use it 40Mb or 50Mb always??

Two possibilities (separated by "------")

first:
----------------------------------------------------------
Typical view of people:

"My application is slow so I need to upgrade the network".

MRTG just showed you this is not true.  There are bottlenecks but
the network isn't one of them.
----------------------------------------------------------


second:
----------------------------------------------------------
You are monitoring a 5-minute window.

Suppose you utilize the full 100 Mbps network for just one second:

counter value = 100,000,000  (some arbitrary number)
<wait 5 minutes>             (somewhere in this 5 minutes you use the net)
counter value = 112,500,000  (increase = 100000000/8 = 12,500,000 byte)

What does MRTG show you?

  112500000-100000000        (counter values)
  -------------------
(time x+300) - (time x)      (time stamps)

  12500000
= -------- = 41666 Bps
       300

It could also show (12500000/300*8=) 333328 bps

So, if you use the network to its maximum capacity for just one out of the
300 seconds per monitoring interval, MRTG will show that you are using an
average of 333 kbps.

Same reasoning will work when you use the network for two seconds
at a 50 Mbps rate, 4 @ 25 and so on.
----------------------------------------------------------

In practice, both these explanations should be taken together.  If I do
a backup, MRTG shows that we're using near to 100 Mbps on the net.  That
means the network *is* the probable bottleneck however I just don't care
enough to upgrade it.  Money is better spent on other hardware such as
disk I/O, CPU, mother boards and interfaces.

HTH
Alex
-- 
Received on my linux server: "Increase the speed of your PC in minutes! Stop
windows from crashing, improve internet security and optimize your computers
performance with just a few easy mouse clicks!"

--
Unsubscribe mailto:mrtg-request at list.ee.ethz.ch?subject=unsubscribe
Archive     http://www.ee.ethz.ch/~slist/mrtg
FAQ         http://faq.mrtg.org    Homepage     http://www.mrtg.org
WebAdmin    http://www.ee.ethz.ch/~slist/lsg2.cgi