[rrd-users] Re: RRA Filesize?

[Alex van den Bogaerdt]

Warnes, Jason  SDH wrote:

> When you create your RRD file, RRD Tool will assign all the space that it
> requires ahead of time for the file.  So if you look at the file size right
> now, that should be as big as it ever gets.
> 
> I'm kind of new to RRD Tool, but this is my understanding of it.  Anyone
> please tell me if I'm wrong.

No, you're not wrong.

Additionally:  the size of this file depends on the size of the
size of each variable.  An RRA is little more than an array of
variables.

If the size of an RRD file needs to be calculated before it is
created, one needs to know the size of each component.

The space used by an RRD is some overhead plus the product of
rows * columns for each RRA in that RRD.

The number of datasources times the number of rows in an RRA
times the number of bytes per entry is what each RRA uses.

Using two small dummy RRDs you can test these sizes.  Create
a RRD with the desired number of datasources and the desired
number of RRAs.  Each RRA should have just one row.

Now create the other RRD with almost identical properties.
One of the RRAs should have two rows.

You'll see that the sizes differ.  They will most likely differ
by 8 * number of DSes.

Use the aquired information to calculate the size of the large
RRD.  Each additional row will cause the same increase.

HTH
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