Werk #8077: New option --split-rrds for --rrd-convert, converts PNP storage type

Check_MK has now a new builtin function for converting legacy-style PNP RRDs from storage type SINGLE, which had been the default for many years, to MULTIPLE, which is the current default since about three years. SINGLE means that all metrics of one host or service are stored in a single round robin database, whereas with MULTIPLE each RRD does contain only one single datasource.

Performance tests have revealed that - other then one might guess - MULTIPLE is not significantly slower. But it has the advantage that new datasources can be added on the fly. This is often needed when new versions of Check_MK introduce new metrics. For that reason Check_MK only fully supports storage type MULTIPLE. When using the Check_MK Micro Core then you have to convert to MULTIPLE, if you do not want to loose your historic metrics, because the CMC does not support SINGLE at all.

Converting RRDs - essentially splitting them up - can be done with PNP4Nagios' shipped utility lib/pnp4nagios/rrd_convert.pl, but that is a bit clumsy to use and very slow. If you have thousands of hosts the conversion can take many days.

For that reason Check_MK now can do the splitting into multiple RRDs during the process of the RRD conversion. This is not only simpler for you. It is also much faster because it uses the native C code of the recent RRDTool. This is how to do the conversion. We assume that you are using Nagios as your monitoring core:

1. Make a backup of the directory var/pnp4nagios/perfdata.
2. Stop the npcd. This avoids RRD updates while the conversion is in progress:

   OMD[mysite]:~$ omd stop npcd
   

3. Start the conversion. The option -v selects verbose output:

   OMD[mysite]:~$ cmk -v --convert-rrds --split-rrds
   

4. Edit the file etc/pnp4nagios/process_perfdata.cfg and change the storage type: `etc/pnp4nagios/process_perfdata.cfg`

   RRD_STORAGE_TYPE = MULTIPLE
   

5. Start the npcd again:

   OMD[mysite]:~$ omd start npcd
   

Notes:

• You can specify host names as arguments to cmk --convert-rrds. The conversion will then only be done for these hosts. But when you start ncpd again and only some of the hosts are being converted, then hosts that do not match the storage type in process_perfdata.cfg will loose their RRD data.
• The splitting and the conversion to the RRD configuration that is setup via WATO with the rulesets Configuration of RRD databases of hosts and Configuration of RRD databases of services will be done at the same time. There is no way to just split. But the Default configuration of PNP4Nagios and of WATO for the RRDs is the same, so if you have changed neither, you essentiall will just split.
• Check_MK will not create any backups of any files! Failed modifications, unlucky RRD configuration and software bugs can lead to data loss. Make sure you have a backup.

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