Hi,
We have a requirement where we need to upgrade OS and for that Elasticsearch will be fresh installed on the nodes. I have a question related to master nodes removal.
We have 3 master nodes as part of the cluster. What approach can I take for removing master nodes from cluster for OS migration and then adding them back after OS migration is done.
Approach 1 - Remove one master node at a time for OS migration
Questions
- Can I remove one master node, following this blog and let the elasticsearch cluster run with 2 master nodes and add the removed master nodes once OS migration is done?
- Will this lead to split brain condition with 2 master nodes?
- Can elasticsearch cluster will work in mixed OS mode? i.e. few master node in CentOS7 and few in RHEL9
Approach 2 - Add more master nodes to cluster with new OS and then start removing master nodes with old OS
Questions
- Do I need to add more master nodes (with required OS) into cluster and then do the removal process one by one of master node (with old OS)?
- If yes, what is the initial number of master nodes I have to add before start removal process considering we have 3 initial master nodes.
- Also how these new master nodes will be added to the voting configuration?
- Do I also need to add master nodes list "discovery.seed_hosts" for data nodes for this approach?
Please let me know your thoughts on the above approaches and which will work better.