[rrd-users] Architecture independence for rrd files

[j.halifax2 at seznam.cz]

>It might be better to create a program to convert RRD files in one go
> (we can already do an XML export/import of course) though this too 

>could be more trouble than it is worth.




I believe so, too. Reads/writes are done usually tens of thousands in

a monitoring period (with load peaks) while changing the architecture 

of the machine is done once a several years...




In addition I believe that everyone who needed to export & import the 

rrd files has written such a tool himself.

;) jh








---------- Původní zpráva ----------
Od: Steve Shipway <s.shipway at auckland.ac.nz>
Datum: 21. 1. 2013
Předmět: Re: [rrd-users] Architecture independence for rrd files

"> I thought it would be a good idea on finding out how to make the rrd
> structure architecture independent, and if it's supposed to be, find
> out what's going on.

I believe Tobi is planning architecture-independence for the RRD file for 
RRDtool 2.x.

Making it arch-independent is not so easy (else it would have been done long
ago as this has been on the cards some time). There are several problems 
relating to the generated C struct which is written to the file as created 
in memory:

1. endian - is it MSB first or LSB first (or middle byte first as in 
windows)
2. 23/64 bit - how big is an integer? This adjusts the size of the struct
3. alignment - does your architecture demand integers be byte-aligned and 
therefore generate padding bytes?
4. compiler peculiarities - some just do it differently at compile time.

The first is actively checked for by RRDTool (looking for different magic 
numbers in the header) and - I think - so is the second. Although it knows 
about them, though, working around it without losing a lot of efficiency 
would be a big problem.

It might be better to create a program to convert RRD files in one go (we 
can already do an XML export/import of course) though this too could be more
trouble than it is worth.

I think there is more discussion on this in the Github area Tobi has set up 
https://github.com/oetiker/rrdtool-2.x

Steve

Steve Shipway
ITS Unix Services Design Lead
University of Auckland, New Zealand
Floor 1, 58 Symonds Street, Auckland
Phone: +64 (0)9 3737599 ext 86487
DDI: +64 (0)9 924 6487
Mobile: +64 (0)21 753 189
Email: s.shipway at auckland.ac.nz
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