Elasticsearch - Add one node to a running cluster

for each index i have 2 shards 0 & 1 and i would like to split my data . This is possible ?

When you add your second node to your cluster, then your data will be automatically "rebalanced" and your data will be replicated.

Presumably, if you were to run

$ curl -XGET localhost:9200/_cluster/health?pretty

then you would see that your current cluster health is probably yellow because there is no replication taking place. You can tell because you presumably have an equal number of assigned primary shards as you have unassigned shards (unallocated replicas).

What will happen when you start the second node in the cluster? It will immediately begin to copy shards from the original node. Once complete, the data will exist on both nodes and this is what you want to happen. As you scale further by eventually adding a third node, you will actually spread the shards across the cluster in a less predictable way that does not result in a 1:1 relationship between the nodes. It's only once you add a third node that you can reasonably avoid copying all of the shard data to every node.

Other considerations:

• Be sure to set discovery.zen.minimum_master_nodes to 2. This should always be set to M / 2 + 1 using integer division (truncated division) where M is the number of master eligible nodes in your cluster. If you don't set this setting, then you will eventually cause yourself data loss.
• You want replication because it gives you higher availability in the event of hardware failure on either node. Due to the above setting with a two node cluster, your cluster would be readonly until you added a second node or the setting was unset, but at least the data would still exist.

how this will effect Kibana performance ?

It's hard to say whether this will really improve performance, but it most likely will simply by spreading the workload across two machines.