For a full list of the recommended operating systems for production deployments, see: Recommended Operating Systems for Production Deployments (page 5). 

## See also: 

Platform Specific Considerations (page 202) 

Use the Latest Stable Packages Be sure you have the latest stable release. 

All releases are available on the Downloads 59 page. The Downloads 60 page is a good place to verify the current stable release, even if you are installing via a package manager. 

Use 64-bit Builds Always use 64-bit builds for production. 

Although the 32-bit builds exist, they are unsuitable for production deployments. 32-bit builds also do not support the WiredTiger storage engine. For more information, see the 32-bit limitations page (page 746) 

## Concurrency 

MMAPv1 Changed in version 3.0: Beginning with MongoDB 3.0, MMAPv1 (page 91) provides collection-level locking : All collections have a unique readers-writer lock that allows multiple clients to modify documents in different collections at the same time. 

For MongoDB versions 2.2 through 2.6 series, each database has a readers-writer lock that allows concurrent read ac- cess to a database, but gives exclusive access to a single write operation per database. See the Concurrency (page 758) page for more information. In earlier versions of MongoDB, all write operations contended for a single readers-writer lock for the entire mongod instance. 

WiredTiger WiredTiger (page 90) supports concurrent access by readers and writers to the documents in a collec- tion. Clients can read documents while write operations are in progress, and multiple threads can modify different documents in a collection at the same time. 

## See also: 

Allocate Sufficient RAM and CPU (page 200) 

## Data Consistency 

Journaling MongoDB uses write ahead logging to an on-disk journal . Journaling guarantees that MongoDB can quickly recover write operations (page 73) that were not written to data files in cases where mongod terminated as a result of a crash or other serious failure. 

Leave journaling enabled in order to ensure that mongod will be able to recover its data files and keep the data files in a valid state following a crash. See Journaling (page 308) for more information. 

Write Concern Write concern describes the guarantee that MongoDB provides when reporting on the success of a write operation. The strength of the write concerns determine the level of guarantee. When inserts, updates and deletes have a weak write concern, write operations return quickly. In some failure cases, write operations issued with weak write concerns may not persist. With stronger write concerns, clients wait after sending a write operation for MongoDB to confirm the write operations. 

