Blank on graphs

[thosen]

Hello,

I'm monitoring a switch with port-channel interface (2x1G) and i'm facing a problem which is sometime there are blank on graph (cf attachment).

It's like if values above 1G can't be displayed/interpreted.

Could it be the switch or is there something to do on graph template ?
Acutally I'm using the In/Out bits (64-bit Counters) template.

Thank you for your help.

Regards,

Tom.

[camerabob]

Try adding more threads in the device setup. Looks like dropped data to me. My two cents.

[RustedKnight]

This is a simple situation to understand. Basically what is happening is that you are having traffic extend beyond what your graph can display. There is a simple way to fix this, all we have to do is make an adjustment to the rrd file. This means we need to log into the server backend because we are going to do some command line work. I'm going to write this up as if your server is linux based because thats what I'm use to. But first we need to document some data. For example the location and name of the rrd file if you click on the little wrench just to the right of the graph it will show you that information. Next fire up a command line and get to the prompt of the server. the first thing you are going to look at is what the max value is currently set at. Run the following command inserting your rrd file path and name where directed.

rrdtool info <Data Source> | grep max

You will probably get outpus something like the following
ds[traffic_in].max = 1.0000000000e+08
ds[traffic_out].max = 1.0000000000e+08

This is the problem, you are not accepting large enough values. this means its time to tweak using the following two commands again inserting your datasource path and file where directed.

rrdtool tune <Data Source> -a traffic_in:1000000000
rrdtool tune <Data Source> -a traffic_out:1000000000

Now run the grep command again and notice the difference. You should get something along the following
ds[traffic_in].max = 1.0000000000e+09
ds[traffic_out].max = 1.0000000000e+09

If you did then give your graph 24 hours soak time and see if it still gaps then let us know if this fixed the problem.

The explanation of what is going on is simple. Your graph is not showing any data for more than 800 megabits per second on the outbound but the inbound is displaying traffic during that time slice because it is below the 800 megabit level. So to fix this we need to adjust the rrd file max value limit. One thing to remember is equipment reports the traffic on that oid in bytes, cacti multiplies it through the use of a cdef expression so when when we adjust the file we need to thing in bytes not bits. That first grep shows this. it reports 1e8 which is the same as 100,000,000 or 100 megabytes per second. Take that times 8 to convert from bytes to bits and you have your 800 megabit point max. So we simply use the rrdtool tune command with the -a configuration to set the traffic in to 1,000,000,000 and then do the same with the traffic out. this then moves the max data point from 100,000,000 to 1,000,000,000 or from 800 megabits to 8 gigabits. I see this is a port channel interface. You will want to sum up the line rate for each interface included in that port channel and ensure that whatever you adjust your level to is greater than the total bandwidth of the interface.

[thosen]

Thank you for your answers.

This is strange because I have others port-channel graphs for this switch and they displayed more than 1Gb and without any blanks.
I have created graphs on the same time and used same graph template.

It seems to be only on this graph.

Regards,
Thomas.

[netniV]

Check your graph values (RRD stored data) see what they are showing.

[thosen]

Thank You RustedKnight !

You find my problem.

But why those values (ds[traffic_in].max and ds[traffic_out].max) are different between graphs created on the same time ?
For exemple, I have one with :

ds[traffic_in].max = 1.0000000000e+10
ds[traffic_out].max = 8.0000000000e+10

[netniV]

The maximum is normally reported by the scripts being called, not set specifically by cacti.