I have recently upgraded my Elastic Search cluster from v5.2.2 to v6.1.2.
I did it using cluster restart process as specified in the Elastic Search guide.
I fired the _cat/segments command and noticed that there are 2 Lucene versions visible in the cluster for the same shard. (Screenshot attached)
Can someone help me with this? Is it a common scenario after upgrading?
I have also observed that the performance of the cluster has degraded. Is Force-Merge an option to improve the performance?
Thanks in advance.