I seen a basic version of marvel is free now. Is there any limitation that marvel is free if only my cluster has less than 5/some x nodes. Or its free irrespective of number of nodes in the cluster?
There is no limit on the number of nodes you can use with a Basic license. The basic license enables all Marvel capabilities, except multi-cluster support (single monitoring cluster holding data from multiple clusters), and configurable Marvel data Retention (managed Marvel history was added in 2.3).
What do you mean by configurable data retention, as far as i know marvel stores each days data in a respective index of that day, and that data will exist until we delete that index.
In Marvel 2.3, we added a long-requested feature that automatically maintains Marvel history indexes:
With a Gold or Platinum license, the retention period is configurable to any number. With the Basic license, it is fixed at the default of 7 days.
Note that the automatic maintenance of Marvel history indexes only applies when you're storing the marvel results locally - if you're using a centralized monitoring cluster, you will need to install the marvel-agent on that cluster or manually manage the history indexes there.