The Check_MK Micro Core now supports a new format when creatingRRD files. Here:
Because now all metrics of a service are stored together in one RRD lessdisk blocks need to be updated when a new value is entered. This savesDisk IO. This is possible because the RRDTool version 1.5 now supportschanging existing RRDs. That way if a check outputs new metrics these canbe added to an existing RRD.
Switch to the new format
The new CMC format is not used automatically - neither for existing norfor 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:
1. Make a backup of your current RRDs (~/var/pnp4nagios/perfdata). You mightbe tended to skip this step as the amount of data can be large. But you havebeen warned.
2. Go to the ruleset Configuration of RRD databases of services (andhosts resp.)
3. 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)
4. Activate Changes - And now your system is in a state where newRRDs will automatically be createdin the new format in ~/var/check_mk/rrd.
5. 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 conversionto these:
OMD[mysite]:~$ cmk --convert-rrds -v server01 server02
Note: This keeps the existing RRDs present in ~/var/pnp4nagios/perfdataand needs lots of diskspace. If you low in diskspace and are bold or if youhave 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 runthe command with the option --delete-rrds at any time later.
Since all of you zigs of gigabytes of RRDs needs to be transformed thiscan take a long time. The good news: you do not need a downtime on yourmonitoring during this period. New RRDs are being used for storing currentdata as soon as they exist so with a bit luck and good disk performance youwill not loose data points.
Old PNP SINGLE format
Note: The new RRD format is almost identical with the format SINGLE thatwas default in PNP4Nagios a long time ago. PNP was not able to alter thelist of metrics that a service did output - however. So whenever the list ofperformance data of a check changed the graphs ended at that point of time.There is currently no direct migration from PNP's SINGLE formatto the new CMC format. But you can go the intermediate step withcmk --convert-rrds --split.