> > Can I add new nodes with the 3.11.6 version to the cluster running with > 3.11.3? >
Technically you can. You'll be able to add 3.11.6 nodes to a 3.11.3 cluster. In fact, the reverse works too in my tests but I personally wouldn't want to do it in production. > Also, I see the SSTable format changed from mc-* to md-*, does this cause > any issues? > Operations like repairs and bootstrap still works on my limited testing. For example, if a 3.11.3 node died then you can bootstrap a replacement. I echo the others' sentiment here and I wouldn't do this in production. CASSANDRA-14861 [1] and CASSANDRA-14096 [2] should give you the motivation to want to upgrade the existing nodes first before expanding the cluster. Cheers! [1] CASSANDRA-14861 <https://issues.apache.org/jira/browse/CASSANDRA-14861> Sstable min/max metadata can cause data loss [2] CASSANDRA-14096 <https://issues.apache.org/jira/browse/CASSANDRA-14096> Repair merkle tree size causes OOM
