Consolidating Jira Instances using CMJ while source and target Jira versions are non-compatible

[Nirmani Kalakheti]

Hello Everyone, 

I have a few questions regarding Jira project migration and using CMJ

We are in the process of consolidation our Jira instances into one Jira DC. We have X no of instances with different versions (7.x). These instances won't match to our target instance Jira 8.x. It is recommended that the source Jira and target Jira should be on the same versions. But, we can NOT upgrade our source instances due to the validation process which would take several months only for upgrade. So we started the importing projects using CMJ without upgrading our source instances. And I did so, as CMJ told that without matching the versions, it should be absolutely fine.

But, during the deployment I got the warning of Version Difference: "The snapshot was created on Jira 7.x and you are deploying to Jira 8.x. Deploying a non-compatible snapshot may result in deployment failure, configuration errors or data loss".

So my questions are:

• What would be the negative result/s by deploying a non-compatible snapshot?
• What does the warning means which said, "in deployment failure, configuration errors or data loss"?
• How do I find if I have deployment failure even though audit says deployed successfully?
• How do I know if there are configuration errors though log says deployed successfully?
• How do I know if there are data losses though log says deployed successfully?
• Do you know if it is okay to export/import projects without the compatible versions of Jira?

I am very nervous if we would lose data or so. Thanks for reading this!

Your help would be really appreciated!

[Nirmani Kalakheti]

Thanks @Daniel Ebers , I did cross-posts for better solutions/answers. 

[Daniel Ebers]

I'd propose to continue the conversation in the other post as some answers and the shared solution with the vendor went there:
https://community.atlassian.com/t5/Jira-questions/Jira-Instance-consolidation-using-CMJ-while-source-and-target/qaq-p/1514357

Please try to avoid cross-posts for better usability.

Cheers,
Daniel