[rrd-developers] Re: RRDtool 1.3.x feature list

[Ian Holsman]

I was thinking about the RRD accelerator page and have a problem with  
a in-memory cache.

something in memory can crash, and could only reside on a single  
machine.
This presents an issue when you have RRD files shared over NFS/SANs.

while most of us probably wouldn't care if we lost a single update,  
losing 10-20 updates could represent an hours
worth of data.

Have you considered creating a directory to put the updates in and  
then have a 'apply' function.

for example.
when I create  'foo.rrd' I would also create a 'foo.upd' directory/file
(so for 60,000 RRDs I would have 60,000 upd directories/files)

when my procallator update comes through (which touches about 1-200  
RRDs) it would just add a single line into the upd directory
foo.upd/<timestamp> and inside it would create the values to be updated.

I'm assuming here that a simple file-create or file-append is much  
faster than a single RRD update, and the update directory could be put
on a separate spindle/disk as well.

the 'apply' function would just read the updates and feed them into  
the RRD in a single operation.. speeding that process up, as processing
10 updates to a single RRD in one shot is faster than applying 10  
updates as separate operations.

you could possibly also fix the graph function so it could do the  
apply before it did the graph.

while this might be slower than a pure in-memory solution, it does  
have greater reliability, and you could always use a ram-disk
for the update directories (or a mysql server)

I'm going to try this approach with my overloaded RRD server this  
month to see if it speeds up the machine.

regards
Ian



On 06/09/2006, at 6:15 AM, Tobias Oetiker wrote:

> I have started to keep a list of features for rrdtool 1.3
>
> http://oss.oetiker.ch/rrdtool-trac/wiki/RRDtool13
>
> cheers
> tobi
>
>
> -- 
> Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten
> http://tobi.oetiker.ch tobi at oetiker.ch ++41 62 213 9902
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--
Ian Holsman
Ian at Holsman.net
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