On Mon, Jan 23, 2017 at 6:06 PM, Simon Hobson <[email protected]> wrote: > Stephen R Guglielmo <[email protected]> wrote: > >> With the above database, I update it once a day with four data points. >> I record MIN, MAX, AVERAGE, and LAST on a weekly basis for 10 years. I >> also record MIN, MAX, AVERAGE, and LAST on a daily basis for 35 days. >> >> My question is: Since the RRAs are not named, if I create 1 month, 1 >> year, and 2 year graphs, will the 1 month graph automatically use the >> more granular RRAs (the "daily" 35-day ones as opposed to the "weekly" >> 10-year ones)? > > Yes, it'll automatically use the "best fitting" RRA - which in most cases > will be the right thing. You can also specify the resolution in your graph > command. > > >> Here is an example `graph` command that I received from the RRD Wizard: >> >> rrdtool graph 'sites-1month.png' \ >> --title 'Sites, 1 Month' \ >> --vertical-label 'Number of Sites' \ >> --width '800' \ >> --height '300' \ >> --full-size-mode \ >> --start end-1m \ >> ... > > > It is recommended to explicitly specify the end time, and to round it to an > integer multiple of the RRA resolution. So, for an RRA with a resolution of 1 > day (86400 seconds), specify the end time as an integer multiple of 86400. > And specify the start time as end-(integer multiple of resolution), and > ideally the multiple will be the number of pixels in the graph which avoids > rescaling the data to fit. > > Longer explanation, RRD will use the RRA which best fits - specifically it'll > pick the RRA(s) providing the most data within the specified timescale, and > if more than one, the one with the highest resolution. So in your case, if > you plot a graph over 36 days then the 1 day RRA won't fill it and it'll > switch to a coarser RRA. for 35 days and below, it'll pick the 1 day RRA as > having the higher resolution. > But there are cases where a coarser resolution may provide more data - though > I don't think they are very common. > > Consider if you aggregated at 2 day and 5 day resolution - contrived but > illustrates the point. There will be times where the 5 day RRA covers a day > later than the 2 day RRA (basically where it's a multiple of 5 days since > unix epoch) - and so the "use the RRA with the most data in the desired > period" method will switch to the 5 day RRA. > For a case like this, you'd need to explicitly specify the RRA to be used, > and your data would stop a day earlier while showing more detail.
Simon, Thank you for the information. It's helpful. If I were to do something like the following: rrdtool create filename.rrd \ --step '86400' \ 'DS:Sites:GAUGE:172800:0:U' \ 'DS:DeletedSites:GAUGE:172800:0:U' \ 'DS:OutdatedSites:GAUGE:172800:0:U' \ 'DS:Users:GAUGE:172800:0:U' \ 'RRA:LAST:0.3:1:3660' This will basically keep every single value entered for 3660 days (~10 years), correct? It won't consolidate any values? I understand this will have increased disk usage in the .rrd file, but are there any other downsides to doing this? Thank you! Steve _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
