In Mongo what is the difference between sharding and replication?

Question

Replication seems to be a lot simpler than sharding, unless I am missing the benefits of what sharding is actually trying to achieve. Don\'t they both provide horizontal sca

Answer 1

Just to put this somewhere...

The most basic way to run mongo is as standalone server.

• You write a config (file or cli options)
• initiate the server using mongod

For this picture, I didn't include the "client". Check the next one.

• A replica set is a set of servers initialized exactly as above with a different config file.
• To link them, we connect to one of them, and initialize the replica set mode.
• They will mirror each other (in the most common configuration). This system guarantees high availability of data.

The initialization of the replica set is represented in the red border box.

• Sharding is not about replicating data, but about fragmenting data.
• Each fragment of data is called chunk and goes to a different shard. shard = each replica set.
• "main" server, running mongos instead of mongod. This is a router for queries from the client.

Obvious: The trade-off is a more complex architecture. Novelty: configuration server (again, a different config file).

There is much more to add, but apart from the words the pictures hold much the same.

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Even mongoDB recommends to study your case carefully before going sharding. Vertical scaling (vs) is probably a good idea at least once before horizontal scaling (hs).

vs is done upgrading hardware (cpu, ram, etc). hs is needs more computers (but could be cheap computers).