We are in the process of migrating from ES 6.4 to 7.9, and around 3 TB of data. I'm looking into reindex API to start the process and do testing. My question is does reindex API will delete the original indexes? for now, I just want to test the cluster and see if alerting works as we expect.
Also, is there any recommended or documented process on how we move from the old cluster to new?