Redis Flex and Auto Tiering enable your data to span both RAM and dedicated flash memory.
| Redis Enterprise Software | Redis Cloud |
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Redis Flex and Auto Tiering in Redis Enterprise Software enable databases to use solid state drives (SSDs) to extend beyond DRAM capacity. Developers can build applications that require large datasets using the same Redis API. Using SSDs can significantly reduce the infrastructure costs compared to only DRAM deployments.
Frequently used data, called hot data, belongs in the fastest memory level to deliver a real-time user experience. Data that is accessed less frequently, called warm data, can be kept in a slightly slower memory tier. Redis Flex maintains hot data in DRAM, keeps warm data in SSDs, and transfers data between tiers automatically.
Redis Flex is based on a high-performance storage engine (Speedb) that manages the complexity of using SSDs and DRAM as the total available memory for databases in a Redis Enterprise cluster. This implementation offers a performance boost of up to 10k operations per second per core of the database, doubling the performance of Redis on Flash.
Just like all-RAM databases, Redis Flex databases are compatible with existing Redis applications.
Redis Flex is also supported on Redis Cloud and Redis Enterprise Software for Kubernetes.
Redis Flex is the enhanced successor to Auto Tiering, generally available as of Redis Enterprise Software version 8.0.2.
Redis database versions support Redis Flex and Auto Tiering as follows:
| Redis database version | Redis Flex | Auto Tiering |
|---|---|---|
| 8.0 and later | ✅ | ❌ |
| 7.4 | ✅ | ✅ |
| 7.2 and earlier | ❌ | ✅ |
Redis Flex requires the Speedb driver, while Auto Tiering can use either RocksDB or Speedb. See Manage Auto Tiering storage engine for more information.
The benefits associated with Redis Flex are dependent on the use case.
Redis Flex is ideal when your:
Redis Flex is not recommended for:
Redis Flex is not intended to be used for persistent storage. Redis Enterprise Software database persistent and ephemeral storage should be on different disks, either local or attached.
When using Redis Flex, RAM storage holds:
All data is accessed through RAM. If a value in flash memory is accessed, it becomes part of the working set and is moved to RAM. These values are referred to as "hot data".
Inactive or infrequently accessed data is referred to as "warm data" and stored in flash memory. When more space is needed in RAM, warm data is moved from RAM to flash storage.
Redis Enterprise Software allows you to configure and tune the ratio of RAM-to-Flash for each database independently, optimizing performance for your specific use case. While this is an online operation requiring no downtime for your database, it is recommended to perform it during maintenance windows as data might move between tiers (RAM <-> Flash).
The RAM limit cannot be smaller than 10% of the total memory. We recommend you keep at least 20% of all values in RAM. Do not set the RAM limit to 100%.
Implementing Redis Flex requires pre planning around memory and sizing. Considerations and requirements for Redis Flex include:
After these requirements are met, you can create and manage both Redis Flex databases and all-RAM databases in the same cluster.
When you begin planning the deployment of a Redis Flex database in production, we recommend working closely with the Redis technical team for sizing and performance tuning.
When running in a cloud environment:
When you begin planning the deployment of Redis Flex in production, we recommend working closely with the Redis technical team for sizing and performance tuning.
On-premises environments support more deployment options than other environments such as:
Redis Flex databases cannot store keys or values larger than 4GB in flash storage.
Keys or values larger than 4GB will be stored in RAM only, and warnings will appear in the Redis logs similar to:
# WARNING: key too big for disk driver, size: 4703717276, key: subactinfo:htable