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What is primary shard in MongoDB?
Each database in a sharded cluster has a primary shard that holds all the un-sharded collections for that database. Each database has its own primary shard. The primary shard has no relation to the primary in a replica set.
What is the purpose of MongoDB sharding?
Sharding is a method for distributing data across multiple machines. MongoDB uses sharding to support deployments with very large data sets and high throughput operations. Database systems with large data sets or high throughput applications can challenge the capacity of a single server.
How does MongoDB scale horizontally?
MongoDB provides horizontal scaling through sharding. MongoDB sharding gives additional capacity to distribute the write load across multiple servers(shards). Sharding enables your MongoDB to distribute the data across multiple servers to handle concurrent client requests efficiently.
Is MongoDB a primary?
The primary is the only member in the replica set that receives write operations. MongoDB applies write operations on the primary and then records the operations on the primary’s oplog. Secondary members replicate this log and apply the operations to their data sets.
Does MongoDB scale well?
A system that scales well will be able to maintain and increase its level of performance under larger operational demands. MongoDB supports horizontal scaling through Sharding , distributing data across several machines and facilitating high throughput operations with large sets of data.
What happens if one shard of MongoDB fails?
If operations can be processed by a single shard, the failure of a single shard will only render some data unavailable. If operations need to access all shards for queries, the failure of a single shard will render the entire cluster unavailable. Changed in version 3.2. Starting in MongoDB 3.2, config servers can be deployed as replica sets.
How does moveprimary move collections in MongoDB cluster?
In a sharded cluster, movePrimary reassigns the primary shard which holds all un-sharded collections in the database. movePrimary first changes the primary shard in the cluster metadata, and then migrates all un-sharded collections to the specified shard. Use the command with the following form:
If the unavailable mongod is a primary , then the replica set will elect a new primary. If the unavailable mongod is a secondary, and it disconnects the primary and secondary will continue to hold all data.
How to rename a shard in MongoDB cluster?
Use CNAMEs to identify your config servers to the cluster so that you can rename and renumber your config servers without downtime. At the end of a chunk migration, the shard must connect to the config database to update the chunk’s record in the cluster metadata.