We have Elasticsearch 6.8 running at the moment and want to migrate it to 7.17.
I have created another cluster with 7.17 running and we would like migrate the indices from 6.8.
what is the best way to do it, I would like to do it without any downtime.
I have already tried reindexing and it works, but this will be a problem when we are doing in PROD.
NOTE: we have no internet or root access on these VMs. so I have downloaded the tars and running both the versions
Why you create another cluster instead of upgrading the current one?
If you want to migrate data from one cluster to another you have basically two options, reindex from remote and using snapshots, if you are still writing in the 6.8 cluster, when you reindex or create a snapshot, the data written after that will not be present in the reindex indice or in the snapshot and you will need to keep doing reindexes and snapshots.
The easiest way would be to upgrade your current cluster, so you would ber able to do a rolling upgrade from the last 6.8.X to the last 7.17.X as described in the documentation.
You also need to check in the Kibana Assistant upgrade if you need to fix something.