Starting multiple nodes do not allocate replica shards - elasticsearch

Question

So, I had just started out with Elasticsearch on my local machine.
I have started 5 instances of Elasticsearch nodes. (simple ./bin/elasticsearch)
curl -s 'localhost:9200/_cat/nodes?v' gives:
host ip heap.percent ram.percent load node.role master name
127.0.0.1 127.0.0.1 5 99 3.13 d m Shirow Ishihara
127.0.0.1 127.0.0.1 7 100 3.13 d m Madame Web
127.0.0.1 127.0.0.1 5 100 3.13 d m Anthropomorpho
127.0.0.1 127.0.0.1 5 100 3.13 d m Paste-Pot Pete
127.0.0.1 127.0.0.1 2 100 3.13 d * Mephisto
My index has 2 primary shards and 5 replicas (total 10 replicas).
I had read that ES automatically scales horizontally and assigns/moves shards to new nodes. However, still all the 10 replicas are unassigned and both the 2 primary shards are in the same node.
curl -s 'localhost:9200/_cat/allocation?v' gives:
shards disk.indices disk.used disk.avail disk.total disk.percent host ip node
0 0b 105.5gb 6.2gb 111.8gb 94 127.0.0.1 127.0.0.1 Shirow Ishihara
0 0b 105.5gb 6.2gb 111.8gb 94 127.0.0.1 127.0.0.1 Paste-Pot Pete
2 318b 105.5gb 6.2gb 111.8gb 94 127.0.0.1 127.0.0.1 Mephisto
0 0b 105.5gb 6.2gb 111.8gb 94 127.0.0.1 127.0.0.1 Anthropomorpho
0 0b 105.5gb 6.2gb 111.8gb 94 127.0.0.1 127.0.0.1 Madame Web
10 UNASSIGNED

Answer 1

You have too few available disk space an ES is actually trying to move away some shards. But all your nodes are on the same machine so there is nowhere else where to move them and they stay unassigned. The used disk space is more than 90% of the total disk size and ES is hitting the the high watermark.
Read here more about this.