A few things you need to know about MongoDB

This article lists some of the mongodb limitations that are confusing to the author, and if you're planning to use MongoDB, at least get to know these limits in advance so you don't have to be caught off guard.

Disk space consumption

This is my first puzzle: MongoDB consumes too much disk space. Of course, this is related to how it is encoded, because MongoDB avoids disk fragmentation problems by pre-allocating large file space. It works like this: When you create a database, a file named [DB name].0 is created, and when more than half of that file is used, a file named "DB name].1" is created again, which is twice times the size of the file. This situation will continue to occur, so files of size 256, 512, 1024, 2048 will be written to disk. Finally, when you create the file again, the size will be 2048Mb. If storage space is a limitation of the project, then you have to consider this situation. The problem has a commercial solution named TOKUMX, which reduces storage consumption by 90% after use. Moreover, in the long run, RepairDatabase and the compact command will help you to some extent.

Data replication through a replica set works great, but there are limitations.

The

copy set strategy for data replication in MongoDB is great, easy to configure and really good to use. But if you have more than 12 nodes in your cluster, you will encounter problems. The copy set in MongoDB has a limit of 12 nodes, here is the description of the problem, you can trace the question to see if it has been resolved.

Master-slave replication does not ensure high availability

Although it is not recommended to be used, MongoDB provides another replication strategy, that is, master-slave replication. It solves the 12 node limit problem, but it creates a new problem: if you need to change the master node of the cluster, then you have to be done by hand, you're surprised? Look at this link.

Do not use the 32-bit version

The

32-bit version of MongoDB is also not recommended because you can only process data of 2GB size. Remember the first limit? This is the description of MongoDB about this limitation.

Consulting fees are very, very expensive (at least for developers and companies in Brazil)

I'm not sure about the rest of the world, but at least the consultancy fee in MongoDB, Brazil, is a sky-price. For the "Lightning Consult" program, the hourly price is $450, and you need to buy at least two hours, in other words, for any company, the price of each consultation is at least $900. This price is too high compared to Redhat and Oracle.

Poor management tools

This is still a headache for beginners, and MongoDB's management console is a lousy one. The best tool I know is Robomongo, which is very handy for developers who use it for the first time.

Learn about the official restrictions

To

my surprise, very few people queried the limitations of the tools they were going to use. Fortunately, MongoDB developers have published a blog with all the limitations of MongoDB, and you can get the information in advance to avoid embarrassment during use.

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