Advanced Redis Information
Redis is a fast, in-memory, caching mechanism that allows Cherwell to quickly exchange data between servers.
Cherwell stores temporary, volatile data into Redis so that each server can pick up where other servers have left off. Redis runs very well on commodity hardware and does not need any hard-drive space because it stores everything in-memory. Redis is an open source database that can run both on Windows and Linux. Download it here.
In earlier versions of Redis, master/slave terminology was used. In later versions of Redis, slave was changed to replica. This documentation uses master/replica terminology for all Redis versions.
Redis is used to share two types of data:
- User session data: Describes the state of the current logged in User. There is an entry in Redis for each of the active sessions on the web. No sensitive data (password or encrypted fields) are stored in Redis. Session data is only stored transiently as Users go from one request to another. All session information is deleted on session expiration, and all information is deleted if Redis is turned off.
- Common application data needed for the application server to work: Application data is stored in Redis for the entire time that the application is running.
Redis Labs Enterprise Cluster
CSM is compatible with Redis Labs Enterprise Cluster (RLEC), the enterprise offering that allows you to simplify your Redis management. In a RLEC environment, many implementation details are simplified. For example, RLEC eliminates the need to manually edit configuration files, manually set up a master/replica environment, or determine how many sentinels you need.
While the documentation in this section is primarily intended written for users who do not use RLEC, it is beneficial for you to understand the underlying technology and the options described in our documentation so you can make decisions appropriate to your specific environment.
If you are using RLEC, we recommend you become familiar with the concepts expressed in the documentation, as they apply in both scenarios. For the few places where RLEC deserves specific considerations, you will see RLEC notes accompanying the documentation.