Hi all, I would like to know the best practices to migrate a mission critical Solr cluster from version 6.x to 8.x without any service shutdown. Is the double upgrade required (mandatory) ? We can introduce another temporary group of machines ro join the cluster, then we may stop the existing nodes one by one once upgrade done... In this case we have different indexes and 2 replicas per shard...
Is it possible to have concurently 2 versions of SolR running in the same cluster? Of course a full reindexing seems to be required , there is no problem we have enough time ( upgrade procedure is not required to be finished in a short time). I would like to have a summary of options available , pros & cons for each one and if possible a few tips & tricks to avoid some pitfalls... If you have good pointers to share and any feedback from production upgrades they will be welcome... Thanks for your help . Kind regards
