perfSONAR User Q&A and Other Discussion

[Ralph Niederberger <>]

Dear Piotr,

thanks for your response. I have read the document you proposed.
Of course I know what utilization means, but the document does not 
answer my question.

see comments inline below.

best regards

Ralph

Piotr Pikusa schrieb:
> Hi Ralph!
>
> In short, please read http://www.gridforum.org/documents/GFD.23.pdf, 
> section 7 and in details section 7.2 to get answer what the utilization 
> is. If you have any questions after reading, please write to the group.
>
>
> Ralph Niederberger wrote:
>   
> > Dear all,
> >
> > I am just in the process of setting up an SQL-MA.
> >
> > There are tables for discards, errors and utilization.
> >
> > Normally I get input and output packets per interface via SNMP.
> > How have the sql tables to be defined to store those values, i.e
> > what is meant with utilization?
> >     
I should respecify my question a little better to be more accurate. 
Within the CISCO web pages:
   
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a008009496e.shtml
   "How To Calculate Bandwidth Utilization Using SNMP"

I have to calculate the utilization using several requests via SNMP. In 
principle it is:
"number of packets coming in/out per interval" divided by  intervall-period

They provide a percentage value, so they multiply by 100 and divide by 
interface speed.

Since the sql tables within perfSONAR SQL-MA have a field valueUnits 
"Bps". I assume I have to
store here the packets (not bits) transfered (in or out) per second. So 
to compute those values,
I have to  start two snmp  requests, ie. at start-time and end-time of 
measurement intervall.
It would be much more convenient to store the Interface counters (in or 
out) only.
A client application could then calculate the utilization itself getting 
all the counters within the intervall
interested in. It would also allow calculating utilization for any time 
intervall, not only the once
measured, since the snmp interface values are updated by default in the 
machine to which I send
my request.

> > Further is the direction of traffic defined by the metadataId, e.g. by 
> > specifying
> > metaid-interface-in and metaid-interface-out?
> >     
I assume that there are different metadata ids for input and output 
measurements, since file
....
has a field <nmwgt:direction>in</nmwgt:direction>
is that correct? Or means utilization always  input+output? But then the 
perfsonarUI tool could
not differeentiate between input and output.

> > And what do I have to store in the db field "value"? Is it the 
> > utilization
> > of the interface, which means before inserting data I have to 
> > calculate this
> > dependend on the last time I stored a value (packets in since last 
> > inserting
> > devided by time since last inserting?
> > Or do I have to store the packet count of the interface only and when
> > requesting infos, the utilization will be calculated dependend on the 
> > time
> > interval I specify within the client request?
> >     
see same discussion above.
I assume valueUnits "Bps" in SQL perfsonar_utilization table means "Byte 
per second", not "bit per second".
Is this correct?
> > many thanks in advance
> >
> > Ralp

--

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Ralph Niederberger
Juelich Supercomputing Centre
Institute for Advanced Simulation

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and member of the
Gauss Centre for Supercomputing
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