OK. I will try this one more time then I will shut up.
The latency tests will not adversely affect the bandwidth tests - so at that level they will at least not affect the agreed purpose of the boxes.
However, at any time bandwidth tests are running a: the network interface will be to some degree be saturated and b: the cpu may also be busy ( b: is especially true for 10 gig ). Both of these will tend to firstly increase observed latency and secondly cause some amount of packet loss.
This is nothing to do with perfsonar per se, just about running iperf and similar tests - or indeed just using your network a lot. (You'd see the same effects on busy disk servers.)
As you increase the number of hosts you test against, you also increase the amount of time your bandwidth tests are running. So you will also increase the amount of time any latency tests are being distorted. (So at the moment, testing against just a handful hosts you might not see a large effect.)
What all this means is that your latency tests will be telling as much if not more about how busy your bandwidth test hosts are rather than the quality of the network between your hosts.
Internet2 and the perfsonar developers know what they are talking about when it comes to network monitoring. They make good recommendations. I don't understand this enthusiasm for doing what they explicitly suggest you do not do.
--Ian
On 12 Jul 2012, at 14:24, Peter Gronbech wrote:
> I agree with Ewan, in that I thought that was the plan agreed at the ops meetings.
> I'm not an expert on perfsonnar so do not know if running both tests would be a problem, but it was not the intension.
>
> Cheers Pete
>
>
>
> --
> ----------------------------------------------------------------------
> Peter Gronbech GridPP Project Manager Tel No. : 01865 273389
> Fax No. : 01865 273418
> Department of Particle Physics,
> University of Oxford,
> Keble Road, Oxford OX1 3RH, UK E-mail : [log in to unmask]
> ----------------------------------------------------------------------
>
>
>> -----Original Message-----
>> From: Testbed Support for GridPP member institutes [mailto:TB-
>> [log in to unmask]] On Behalf Of Ewan MacMahon
>> Sent: 12 July 2012 10:44
>> To: [log in to unmask]
>> Subject: Re: perfSonar machine in Sheffield
>>
>>> -----Original Message-----
>>> From: Testbed Support for GridPP member institutes [mailto:TB-
>>> [log in to unmask]] On Behalf Of Ian Collier
>>> Sent: 12 July 2012 10:37
>>>
>>> You don't want bandwidth and latency tests running on/against the same
>>> machine. (The bandwidth tests running are likely to make the latency
>>> results meaningless.)
>>>
>>
>> Indeed, I thought the plan was for the original six sites with
>> a pair of boxes to run both, and the sites with just the one
>> new machine (that was going to be a gridmon node) would now be
>> set up as a PerfSonar bandwidth box, and those sites just wouldn't
>> have latency measurements.
>>
>> In other words, I think Elena's current configuration is what I'd
>> expect it to be.
>>
>> Ewan
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