Alex van den Bogaerdt wrote: > > Interestingly, I've noticed that the same graph needs increasing >> amount of memory as you go back in time - ie using coarser >> consolidations. > > >Careful planning of your RRD may save memory. > >If you only have RRAs spanning 5 minutes per row, and if you are looking >at a year's worth of data, that's 105120 rows.
Got four consolidations : 5 minutes (1 sample) for 48hr 1/2 hour for 14 days 2 hour for 62 days 12 hour for 720 days And I plot graphs for last 24hour, 7days, 30 days, and 365 days. I wrote down the VM reached for each graph, and found that as the time period went up, so did the memory requirements - with the years graph using something like 50% more memory than the days graph, with the others fairly evenly spaced in between. >This mail does not describe all of the memory used. Also, the information >is simplified (and thus slightly wrong). However, the biggest memory >consumer is the data in DEF and CDEF. The biggest improvement you can >make is to have the input data (RRAs, fetched by DEF) in the resolution >you are going to need. > >Make sure you fetch the right data. There's a huge difference between >"--start end-24h --end now" run at midnight and "--start end-24h --end 00:00". >The difference is "--end now" not being equal to "--end 00:00" unless >you happen to run the commend _exactly_ at midnight. > >If you have 5-minute RRA and 1-hour RRA: >Selecting "--start end-7d --end now" just after the whole hour results in >fetching data from the 5-minute RRA. 7*24 hours plus one more interval (to >cover the difference between 'now' and the whole hour), or 2017 rows. > >Selecting "--start end-7d --end 00:00" may result in fetching data from >the 1-hour RRA, 168 rows. This depends on more than just start and end >times but if you're displaying 168 pixel columns (so: --width 168) then >this RRA would be selected. Now that is interesting. All the graphs are done as end=now and start=end-<24H|7D|31D|365D> I had assumed that all the graphs would use the right consolidation because the higher resolution ones will not cover the requested period. What I think you are saying is that if I kept the 5 minute samples for 8 days, then it would use the 5 minute samples, not the 1/2 hour consolidation so as to best fill the graph. Am I right in thinking it will never use two separate consolidations (eg the 2 hour one for the bulk of the months graph plus the latest 5 minute samples to fill in the gap at the end) ? > >Also, you may not want midnight to midnight. You probably want UTC 00:00 >to UTC 00:00 to view days. >To view weeks, you do not want sunday to sunday, you want thursday 00:00 UTC >to thursday 00:00 UTC. At least for the daily and weekly graphs, we pretty well need graphs ending about now - and tbh I can't be bothered working out what the last period end time should be for any particular graph, the odd blank pixel doesn't bother us. >In general: make sure start and end times match your RRA, >and the amount >of pixels matches the amount of rows. That's one where I probably could improve things. -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://lists.ee.ethz.ch/rrd-users WebAdmin http://lists.ee.ethz.ch/lsg2.cgi
