For going from 2.1 to 2.5, you will have to use the option of import a cluster in v2.5.2.  Firstly, you need to deploy a new VM which has IIQ 2.5.2.  Then import a cluster that is being monitored by the earlier version of InsightIQ. All previously collected data for the cluster is then migrated to the new version of InsightIQ. So both VMs (v2.1 amd v2.5.2) need to turned on when you import.  Thereafter you can upgrade to 3.0.1
Hi All,   I am planning to upgrade InsightIQ from 2.1 to 3.0 and it seems to be like a two step process, upgrade to 2.5 and then 3.0.  Is there a way to use the performance and file data gathered by IIQ 2.1 with 3.0 ?   Thank you 
InsightIQ 2.1 to 3.0 upgrade