The comparison between MongoDB and Redis

Both MongoDB and Redis are NoSQL, using structured data storage. There are some differences between the two in the usage scene, which is mainly due to the process of the memory mapping, and the persistence processing method is different.

MongoDB recommended cluster deployment, more considering the cluster scenario, Redis is more emphasis on process sequential write, although the support cluster, but also limited to the master-slave mode.

Compare indicators	MongoDB (v2.4.9)	Redis (v2.4.17)	Comparison notes
Implementation language	C++	C + +	-
Agreement	BSON, Custom Binary	Class Telnet	-
Performance	Memory dependent, higher TPS	Memory dependent, TPS very high	Redis is better than MongoDB
operability	Rich data expression, index, most similar to relational database, support rich query statement	Data-rich, less IO	MongoDB is better than Redis
Memory and Storage	Suitable for large data volume storage, dependent on system virtual memory, image file storage, high memory consumption ratio, the official recommended independent deployment in 64-bit system	REDIS2.0 supports virtual memory features (VMS) Beyond physical memory limits, data can be set to timeliness, similar to Memcache	Different application scenarios
Availability of	Support Master-slave,replicatset (internal use of Paxos election algorithm, automatic failback), auto sharding mechanism, blocking the failover and slicing mechanism to the client	Rely on the client to implement the distributed read and write, master-slave replication, every time from the node reconnect to the primary node to rely on the entire snapshot, no incremental replication; auto sharding is not supported, need to rely on the program to set the consistency hash mechanism	MongoDB is better than Redis; On a single point problem, MongoDB application is simple, relative user transparent, Redis is more complex, need the client to actively solve. (MongoDB is typically combined with replicasets and sharding, replicasets focus on high availability and high reliability, sharding focus on performance, horizontal scaling)
Reliability	Support for persistence in Binlog mode (MySQL-like) since version 1.8	Rely on snapshots for persistence; AOF enhances reliability and enhances performance while impacting access
Consistency	Transactions are not supported, guaranteed by the client	Support transactions, more brittle, only ensure that operations in the transaction are executed sequentially	Redis is better than MongoDB
Data analysis	Built-in data analysis capabilities (MapReduce)	Not supported	MongoDB is better than Redis
Application Scenarios	Increased access efficiency for massive data	Performance and operation of smaller data volumes	MongoDB is better than Redis

Category: Redis

Http://www.cnblogs.com/chinesern/p/5581422.html

1\redis and Mongodb,mysql


Redis is a database that completely stores data in memory, uses disk for persistence purposes only, the Redis data all exists memory, writes to disk periodically, when memory is not enough, can choose the specified LRU algorithm to delete data, persistence is using RDB or aof way.


MongoDB is a document-type non-relational database, MongoDB is more like MySQL, support field index, cursor operation, the advantage is that the query is more powerful, good at querying JSON data, can store large amounts of data, but does not support transactions.


All of MongoDB's data is actually stored on the hard disk, and all the data to be manipulated is mapped to an area of memory in a mmap way.
MongoDB then modifies the data in this area to avoid fragmented hard disk operations.
As for the contents of mmap flush to the hard disk is the operating system, so if, MongoDB in memory after modifying the data, MMAP data flush to the hard disk before the system down, the data will be lost.


Mysql:
Both the data and the index are stored on the hard disk. To be swapped into memory when it is to be used. Ability to handle data that is far more than the total amount of memory.


Data volume and performance:
When the physical memory is sufficient, the Redis>mongodb>mysql
Both Redis and MongoDB use virtual memory when physical memory is not enough.
In fact, if Redis is going to start virtual memory, it's obviously either adding a memory bar, or you're changing the database.
However, MongoDB is not the same, as long as the business can guarantee that the hot and cold data read and write ratio, so that the thermal data in physical memory, mmap exchange less.
MongoDB is still capable of guaranteeing performance. Someone uses MongoDB to store data on the upper T.
Mysql,mysql doesn't have to worry about the amount of data that is related to memory.




Redis transaction support is weak and can only guarantee continuous execution of each operation in a transaction
MongoDB does not support transactions


MongoDB has built-in data analysis capabilities (MapReduce) and Redis does not support


Redis can only use single threads and performance is limited by CPU performance

The comparison between MongoDB and Redis