[rrd-users] Increase RRA Size

[Alex van den Bogaerdt]

----- Original Message ----- 
From: "Bigras, Guy" <gbigras at telesat.com>
To: <rrd-users at lists.oetiker.ch>
Sent: Thursday, May 06, 2010 11:08 PM
Subject: [rrd-users] Increase RRA Size


> Hi there,
>
> I'd like to add a new RRA to the RRD file.  Can't figure out how to do it.

and you don't need to.

> Here's some background information:
>
> I'm using Cacti 0.8.7e with rrdtool verion 1.3.8-1.
>
> I've setup my RRDs to use four custom RRAs instead of the default ones. 
> The major difference is that there is no data point averaging being done.

If you think that you store data with no alteration whatsoever, be careful. 
Only in very specific circumstances this will be true. You really need to 
study normalization and consolidation. See further on.

> Here is my RRA setup (5 minute polling interval):

[partially cut away]
> RRA1: Daily> Consolidation: average> steps: 1
> RRA2: Weekly> Consolidation: average> steps: 1
> RRA3: Monthly> Consolidation: average> steps: 1
> RRA4: Yearly> Consolidation: average> steps: 1
> rows: 109440
> Timespan: 31536000

All your RRAs have consolidation function average and steps==1. That's 
useless. RRAs 1,2 and 3 just contain parts of what RRA 4 contains.

> The reason there is no averaging is because the powers from above do not 
> want to loose any data point.  They want to be able to zoom into any 
> "peak" on the graph and be able to look at the real data as opposed to an 
> average.

That explains why you would have one large RRA with steps==1 step. But it 
doesn't explain why you have the other 3 setup as you have. Study the 
tutorials, visit my site http://www.vandenbogaerdt.nl/rrdtool/


> However now they want to be able to keep more than a year's worth.  Hard 
> drive space is not an issue so I've opted for a ten year RRA.  I just 
> don't know how to modify an existing RRD file to incorporate these 
> changes.  I've tried some scripts to export data and import back but it 
> doesn't seem to work.

10 years = 7*365 days + 3*366 days (leap years) * 288 rows = 1052064 rows.

Increase the size of RRA 4. That RRA contains the largest amount of 
information. Any rows you add do not magically contain information you 
didn't have before, but as soon as they are there, you can start building 
history.

You already have 109440 so grow the RRA by 942624 rows.  And don't forget 
that a new RRD is built, you need to check that RRA (to see if it really is 
what you want) and then copy it over the old one.  And don't forget to 
backup the previous one first.

You can keep the other RRAs (useless, but not in your way) or you can setup 
the RRD in a different way. Explaining how would be a bit too much right 
now. You could also consider to hire someone to help you, tutor you, or 
both.

Regards,
Alex