[mrtg] Graphing disk iowait on Debian using mrtg and routers2

Steve Shipway s.shipway at auckland.ac.nz
Mon Aug 2 23:21:04 CEST 2010

> I'm trying to graph iowait on Debian but having trouble finding
> examples. Is it best to use an
> iostat bash script or the SNMP counter (.
> The SNMP counter seems to be an ever increasing value. I thought it
> might be the number
> of seconds the CPU has waited for, but I'm not sure how to use this
> value?

If I remember right, this is a counter of CPU seconds.  The problem you get is when you have multiple CPUs and need to normalise this to a percentage.... 

Graph it as a normal counter, which results in a calculated seconds per second, and use a Factor[] of 100 to give you a percentage on a single-CPU system.  If you have a dual CPU system, use a factor of 50 (100/cpus) and so on, and set ShortLegend[] to %.


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