[mrtg-developers] Calculating 95th percentile

[Jo Rhett]

You have a problem in your script.  The 95th percentile function  
works perfectly fine.  I don't have time to debug your script but I  
did have time to give you a better method ;-)

On Oct 10, 2007, at 9:54 AM, Westlake, Simon wrote:

> Would that actually perform the correct function though? Wouldn't  
> it also return the same problematic data?
>
> --
> Simon Westlake
> Network Engineer
> Desk: (414) 908-4791
> Cell: (414) 688-7956
>
>  -----Original Message-----
> From: 	Jo Rhett [mailto:jrhett at svcolo.com]
> Sent:	Wednesday, October 10, 2007 12:35 PM Eastern Standard Time
> To:	Westlake, Simon
> Cc:	mrtg-developers at lists.oetiker.ch
> Subject:	Re: [mrtg-developers] Calculating 95th percentile
>
> Much simpler to just do this:
>
> CDEF:pctbits=ds1bits,ds0bits,MAX
> VDEF:pct=pctbits,95,PERCENT
>
> On Oct 10, 2007, at 9:06 AM, Westlake, Simon wrote:
>> Hello all,
>>
>> I'm attempting to write a script to calculate 95th percentile usage
>> using RRD files generated using MRTG. I'm using PHP and  
>> PHP4RRDTool in
>> order to pull the information and calculate it and I'm running  
>> into an
>> issue which has maybe been hidden from me in the past as I use MRTG
>> as a
>> collector for my RRD files.
>>
>> A quick rundown of my method:
>>
>> I have a loop that goes through and pulls 5 minute intervals of data
>> from the RRD file (by doing --start -10m --end -5m for example, and
>> moving backwards in steps of 5) for the last calendar month. It adds
>> this data to an array, sorts it from smallest to largest, strips
>> the top
>> 5% and calculates the average.
>>
>> The script itself seems to work fine, but the data I get returned
>> seems
>> weird.
>>
>> After reading the RRD documentation, it appears that I should be
>> able to
>> pull the information I want by using the following command:
>>
>> $opts = array ( "AVERAGE", "--end", "-$timeframe", "--start",
>> "-$start");
>>
>> Where the $opts array is an array of the options to send. This
>> works and
>> gives me a value, however, the values seem to repeat identically.  
>> Here
>> is a (somewhat brief) example of the data returned over a series of 5
>> minute queries:
>>
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 33748465.7228
>> 34784619.7841
>> <34784619.7841 repeats many times>
>> 34784619.7841
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>> 34993760.8949
>>
>> This seems wrong to me - even as an average, I would not be seeing
>> identical values over separate 5 minute intervals.
>>
>> I have tried various changes to see if I receive different
>> information,
>> and I do not.
>>
>> Am I missing something blindly obvious here? Shouldn't different 5
>> minute intervals return different information?
>>
>> --
>> Simon Westlake
>> Time Warner Cable Business Class
>> Network Engineer
>> Ph: 414.908.4791 | Cell: 414.688.7956
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>>
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>
> -- 
> Jo Rhett
> senior geek
>
> Silicon Valley Colocation
> Support Phone: 408-400-0550
>
>
> This E-mail and any of its attachments may contain Time Warner
> Cable proprietary information, which is privileged, confidential,
> or subject to copyright belonging to Time Warner Cable. This E-mail
> is intended solely for the use of the individual or entity to which
> it is addressed. If you are not the intended recipient of this
> E-mail, you are hereby notified that any dissemination,
> distribution, copying, or action taken in relation to the contents
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> the sender immediately and permanently delete the original and any
> copy of this E-mail and any printout.

-- 
Jo Rhett
senior geek

Silicon Valley Colocation
Support Phone: 408-400-0550