How do you (not how do I) calculate 95th percentile?
Tom Sands
tsands at rackspace.com
Wed Feb 22 18:50:34 UTC 2006
Jo Rhett wrote:
> I am wondering what other people are doing for 95th percentile calculations
> these days. Not how you gather the data, but how often you check the
> counter? Do you use averages or maximums over time periods to create the
> buckets used for the 95th percentile calculation?
>
We use maximums, every 5 minutes.
> A lot of smaller folks check the counter every 5 min and use that same
> value for the 95th percentile. Most of us larger folks need to check more
> often to prevent 32bit counters from rolling over too often.
Actually, a lot of people do 5 minutes... and I would say that larger
companies don't check them more often because they are using 64 bit
counters, as should anyone with over about 100Mbps of traffic.
Are you larger
> folks averaging the retrieved values over a larger period? Using the
> maximum within a larger period? Or just using your saved values?
>
In our setup, as with a lot of people likely, any data that is older
than 30 days is averaged. However, we store the exact maximums for the
most current 30 days.
> This is curiosity only. A few years ago we compared the same data and the
> answers varied wildly. It would appear from my latest check that it is
> becoming more standardized on 5-minute averages, so I'm asking here on Nanog
> as a reality check.
>
> Note: I have AboveNet, Savvis, Verio, etc calculations. I'm wondering
> if there are any other odd combinations out there.
>
> Reply to me offlist. If there is interest I'll summarize the results
> without identifying the source.
>
--
------------------------------------------------------
Tom Sands
Chief Network Engineer
Rackspace Managed Hosting
(210)447-4065
------------------------------------------------------
More information about the NANOG
mailing list