I started playing for Splunk Metrics rollups and but then tried to step out of the box and got a “Failed to apply rollup policy to index=’…’. Summary span=’7d’ cannot be cron scheduled” error.
Here is the interesting part: your rollup span value is limited only to the values available in the UI drop-down (no matter which method of configuration you are using).
The options that you can use are:
|Minute Span||Hourly Span||Daily Span||Notes|
If you will try to use any other value you will see the following error in the splunkd.log:
12-12-2022 14:04:08.645 +1100 ERROR MetricsRollupPolicy [12181677 TcpChannelThread] - Failed to apply rollup policy to index='...'. Summary span='7d' cannot be cron scheduled.
This is not (as of 15/12/2022) a documented “feature”.