The Check_MK Micro Core now supports a new format when creating
RRD files. Here:
LI:RRD files are kept below the new directory ~/var/check_mk/rrd.
LI:All metrics of one service are kept in one RRD
Because now all metrics of a service are stored together in one RRD less
disk blocks need to be updated when a new value is entered. This saves
Disk IO. This is possible because the RRDTool version 1.5 now supports
changing existing RRDs. That way if a check outputs new metrics these can
be added to an existing RRD.
Switch to the new format
The new CMC format is not used automatically - neither for existing nor
for new sites. The default for new sites might be changed in future, though.
Switching your site to the new CMC format is done in the following steps:
Make a backup of your current RRDs (~/var/pnp4nagios/perfdata). You might
be tended to skip this step as the amount of data can be large. But you have
Go to the ruleset Configuration of RRD databases of services (and
Create a rule for some (or all) hosts with the setting
RRD storage format: One RRD per host/service (saves disk IO, only with CMC)
Activate Changes - And now your system is in a state where new
RRDs will automatically be created
in the new format in ~/var/check_mk/rrd.
In order to migrate the existing RRDs use the following command:
OMD[mysite]:~$ cmk --convert-rrds -v
It is also possible to specify a list of hosts and limit the conversion
OMD[mysite]:~$ cmk --convert-rrds -v server01 server02
Note: This keeps the existing RRDs present in ~/var/pnp4nagios/perfdata
and needs lots of diskspace. If you low in diskspace and are bold or if you
have a backup (even better) you can directly delete the PNP format RRDs:
OMD[mysite]:~$ cmk --convert-rrds --delete-rrds -v
If you decided not to delete the old RRDs in the first place you can run
the command with the option --delete-rrds at any time later.
Since all of you zigs of gigabytes of RRDs needs to be transformed this
can take a long time. The good news: you do not need a downtime on your
monitoring during this period. New RRDs are being used for storing current
data as soon as they exist so with a bit luck and good disk performance you
will not loose data points.
Old PNP SINGLE format
Note: The new RRD format is almost identical with the format SINGLE that
was default in PNP4Nagios a long time ago. PNP was not able to alter the
list of metrics that a service did output - however. So whenever the list of
performance data of a check changed the graphs ended at that point of time.
There is currently no direct migration from PNP's SINGLE format
to the new CMC format. But you can go the intermediate step with
cmk --convert-rrds --split.
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