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What happens when I enable balancing in MongoDB?
When you enable balancing for a collection, MongoDB will not immediately begin balancing data. However, if the data in your sharded collection is not balanced, MongoDB will be able to begin distributing the data more evenly. To enable balancing on a collection, connect to a mongos with the mongo shell and call the sh.enableBalancing () method.
What is the definition of replication in MongoDB?
Replication in MongoDB¶. A replica set is a group of mongod instances that maintain the same data set. A replica set contains several data bearing nodes and optionally one arbiter node.
What happens If MongoDB migrates during a backup?
If MongoDB migrates a chunk during a backup, you can end with an inconsistent snapshot of your sharded cluster. Never run a backup while the balancer is active. To ensure that the balancer is inactive during your backup operation: Set the balancing window so that the balancer is inactive during the backup.
Can a load balancer sit behind a replica set?
Within a replica set having a load balancer is discouraged because the load balancer should be aware about the actual primary server and also it should know about read preferences in the cluster. So the answer given about the firs question is that no, it is not possible to have an external load balancer over a replica set cluster.
What’s the default chunk size for a Mongo cluster?
Connect to any mongos in the cluster using the mongo shell. Use the following operation to determine if the balancer is running: The default chunk size for a sharded cluster is 64 megabytes.
How to see if balancer is enabled in sharded cluster?
To see if the balancer is enabled in your sharded cluster , issue the following command, which returns a boolean: You can also see if the balancer is enabled using sh.status () . The currently-enabled field indicates whether the balancer is enabled, while the currently-running field indicates if the balancer is currently running.
Can you have multiple Mongos instances in a cluster?
You can have multiple mongos instances for better load balancing. For example, in your production cluster, you can have one mongos instance for each application server. Now here you can use an external load balancer, which will redirect your application server’s request to appropriate mongos instance.
What does the Mongos service do in MongoDB?
mongos for “MongoDB Shard,” is a routing service for MongoDB shard configurations that processes queries from the application layer, and determines the location of this data in the sharded cluster, in order to complete these operations.