[rrd-developers] more on version

[Jake Brutlag]

Tobias Oetiker wrote:
> you got a point there ... the code has a check for version 2 and 3
> but I have not seen anything for 1 ... so should I just bump up the
> minimal dump version required, or do you want to look at it more
> closely ?   

After investigation, it is indeed case (as it always been) that 1.1.x
restore CANNOT read a version 1 dump file. Of course, 1.1.x dump
will never generate version 1 dump file (it marks the dump with
RRD_VERSION,
currently 3), even if the binary file being dumped is version 1.

1.1.x can read and/or update any version of binary RRD files. In fact, 
by default, 1.1.x create tries to create version 1 binary RRD files
unless 
a higher version is required by a specific feature (this was broken in
the case of COMPUTED data sources, but I fixed it during the checkin for
the updatev interface). I don't if the developer of version 3 (Sasha)
intends
to preserve this default on create (to date, it is still in place).

Basically, dump file and binary file versions are treated differently.

For those code sleuths, you will note that there are some functions in 
rrd_restore.c which refer to a version 1.0.28 patch. Aberrant behavior
detection
was originally implemented in a patch to 1.0.28. This patch included
changes
to rrd_dump and the dump file was marked version 2. However, this
version 2
isn't 100% compatible with what we know today as the version 2 dump
format.
These functions in rrd_restore bridge this gap. In the future, they
should be able
to be removed, because the 1.0.28 aberrant behavior patch is no longer
available
and was not widely distributed to begin with.

Jake Brutlag
Network Analyst
Microsoft MSN 

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