[mrtg] Target and its mapping to RRD

[Daniel McDonald]

On 6/28/11 9:09 AM, "Daniele Sluijters" <d.sluijters at betterbe.com> wrote:

> Hello,
> 
> I'm trying to build a system the company I work for that collects data through
> MRTG, stores it in RRD's and is then graphs on-demand through a web interface.
> 
> However, I'm running into a few things I can't figure out, namely how the
> Target[] line maps to RRD.

One to one.
> 
> For example, is it possible to query more than a two-value pair? RRD can store
> multiple DS's, I was just wondering if something like this would translate to
> 4 DS's:
> Target[network]; oid1&oid2:community at hostname, oid3&oid4:community at hostname

MRTG always uses two DS's.
 
> Another thing I can't exactly figure out is what happens with this:
> Target[network]; oid1&oid2:community at hostname+oid3&oid4:community at hostname
> Does that result in two DS's where ds0 contains oid1+oid3 and ds1 contains
> oid2+oid4

Yes.  If oid1 and oid2 are both monotonically incrementing counters, the
rollover detection is problematic in this case.

> or something else?
> 
> Is it even possible to use such "complex" Target-lines with RRD as a backend?

Yes, you can poll oid1 and oid3 with one target, and oid2 and oid4 with a
second target, then combine them with a front-end like routers2.cgi.  I
often use the stacked graphs for this precise purpose.

> 
> Kind regards,

-- 
Daniel J McDonald, CCIE # 2495, CISSP # 78281