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 Post subject: How to setup RRAs
PostPosted: Wed Jun 05, 2019 11:23 pm 
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Joined: Wed Jun 05, 2019 11:18 pm
Posts: 1
I just asked this on rrd-users and I thought asking it here also since rrd-users does not really get a lot of replies.

I have gone through years of rrd-users mails but still have not solved my problem. Here is what I am thinking right now.

I want to have a sample step size of 3600 seconds:
and I need these RRAs

1. One-day coverage sampled every hour
3600(step)*24(hours)=86400 sec. Add a little padding
3600*25=90000
90000(coverage)/3600(step) = 25 PDPs
RRA:AVERAGE:0.5:1:25

2. One-week coverage averaged every day (24 hours)
7(days)*24(hours)*3600(step)=604800 Add a little padding
7(days)*25(hours)*3600(step)=630000
630000(Coverage)/3600(step) = 175
RRA:AVERAGE:0.5:24:8 # 8*24=192 > 175

3. One-month coverage averaged every week (7 days)
30(days)*24(hours)*3600(step)=2592000 Add a little padding
30(days)*25(hours)*3600(step)=2700000
2700000(Coverage)/3600(step) = 750
RRA:AVERAGE:0.5:7:108 #7*108=756 > 750

4. One-year coverage averaged every 30 days
365(days)*24(hours)*3600(step) Add a little padding
365(days)*25(hours)*3600(step) = 32850000
32850000/3600 = 9125
RRA:AVERAGE:0.5:30:305 # 30*305=9150>9125

I think I am making this much harder for me than it really is and I am somehow thinking of the RRA setup in a too much of a complex way. That´s why I was hoping some genius here could help the needy by maybe documenting a how-to on setting up RRAs. The tutorial on the rrdtool website is not good enough to explain a generic RRA setup. Also missing from the rrdtool website is how to understand GPRINT and PRINT. I am having problems with that also, but more on that later.....


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 Post subject: Re: How to setup RRAs
PostPosted: Thu Jun 06, 2019 1:37 pm 
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Joined: Wed Mar 01, 2017 2:34 pm
Posts: 65
You got the consolidated data points wrong.
Since you want one hour step size, you can do the math without any calculator. It's intuitive, if your brain can calculate hours, days, weeks and months and you want to use these as interval.
Remember: the next to last parameter is the number of primary data points (PDP) consolidated in the RRA. You answer the question: "how many PDP intervals must I have to get my consolidated interval?"
The last parameter is the number consolidated data points (rows) you want to keep. You answer the question: "how many (consolidated) intervals do I want to keep?"

1. One-day coverage sampled every hour
We want 1 PDP every hour, which is 3600 seconds. The generic RRD interval is 1 second. This means our step size is 3600, because we want 1 step (or PDP) every 3600 seconds.
Consolidation: 1 - these are the PDP
Rows: One day is 24 hours. One data point is 1 hour, so we need 24 data points. Take one more => 25.
RRA:AVERAGE:0.5:1:25

2. One-week coverage averaged every day (24 hours)
Consolidation: 1 day are 24 hours are 24 data points to consolidate
Rows: One week are 7 days, so we need 7 data points. Take one more => 8.
RRA:AVERAGE:0.5:24:8

3. One-month coverage averaged every week (7 days)
Consolidation: 1 week are 7 days are 7*24=168 hours are 168 data points to consolidate.
Rows: one month are 5 weeks
RRA:AVERAGE:0.5:168:5

4. One-year coverage averaged every 30 days
Consolidation: 30 days are 30*24=720 hours are 720 data points to consolidate.
Rows: 30 days are 1 month, 1 year are 12 months are 12 data points. Take one more => 13
RRA:AVERAGE:0.5:720:13


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