adding Shard in runtime to MongoDB

Question

We have some servers that serve a specific amount of data (5TB).

The problem is that we have lack in space o the servers and we want to add another server. The question is, what'll happend when I'll add the new shard while all the other servers already running? Will MongoDB be possible to transfer the data to the new server?

Answer 1

You were commented on right away and the response is correct. What will simply happen is that the balancer will periodically attempt to re-allocate chunks across the available shards, including the new one.

The process is automatic after the shard is added so yes is is possible to transfer new data to the server.

Perhaps the main consideration (as pointed to in the document link) is that the balancer is applied on one instance of mongos you have running and of how the balancer behaves. A lot will depend on your configutation, but for more information read the following document in addition:

http://docs.mongodb.org/manual/core/sharding-balancing/#sharding-balancing-internals