Script memory

[mac_fly]

Hello,
I have two data :
total memory
free memory

I would like to graph the used memory. I know that i have to do a simple subtraction but how to do that in cacti ?

thanks.

[Linegod]

Read these two articles:

http://docs.cacti.net/node/528
http://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html

[mac_fly]

Thanks, i read the article but i hava a problem.
So when the cedf is like the first picture the result is good but when is like the second picture the result isn't good. Cacti do an addition.

Sorry for my poor english.
Any idea ?

[mac_fly]

Nobody have an idea ?

[gandalf]

For a graph with only a single data source, the second cdef will ALWAYS yield "0" as a result.
Reinhard

[mac_fly]

Hello,
I have two datasource :
+ free memory
+ total available memory

and i want the used memory so i have to subtract :
total available memory - free memory = used memory

But how can i do that ?

[gandalf]

Hello,
I have two datasource :
+ free memory
+ total available memory

and i want the used memory so i have to subtract :
total available memory - free memory = used memory

But how can i do that ?

Assuming, that
a = free
b = total,
the cdef would be
cdef = b,a,-
Reinhard

[mac_fly]

Assuming, that
a = free
b = total,
the cdef would be
cdef = b,a,-
Reinhard

Thanks gandalf,

Yes exactly but it work just when b is a value and not a datasource.(See screenshot).

[Maestro_Ba]

Hi. I made a template+script that shows the free memory and the total memory.
http://forums.cacti.net/viewtopic.php?p=142813

But the script I made also returns the used memory, I just chose not to graph it. Just make the appropriate changes.