Redis Flex

{{<note>}} This page applies to Redis Enterprise for Kubernetes version 8.0.2-2 and later. If you use version 7.22.2-22 or earlier, see Auto Tiering. {{</note>}}

Overview

[Redis Flex]({{< relref "/operate/rs/databases/flash" >}}) (previously known as Redis on Flash) extends your node memory to use both RAM and flash storage. Solid state drives (SSDs) store infrequently used (warm) keys and values, while RAM stores frequently used (hot) keys and values. This approach improves performance and lowers costs for large datasets.

Redis Flex provides automatic RAM management and improved performance compared to Auto Tiering.

{{<note>}} For best performance, use NVMe (non-volatile memory express) SSDs. {{</note>}}

Redis Flex vs Auto Tiering

{{<warning>}} Redis Flex is not supported for [Active-Active databases]({{< relref "/operate/kubernetes/active-active" >}}). {{</warning>}}

Before creating your Redis clusters or databases, these SSDs must be:

The earlier implementation of Redis Flex is called Auto Tiering, which is available in Redis versions earlier than 8.0.

The operator automatically selects the appropriate implementation based on your Redis version:

• Versions 7.22.2-22 and earlier: Auto Tiering
• Versions 8.0.2-2 and later: Redis Flex

Redis Flex differs from Auto Tiering in the following ways:

Redis Flex (8.0.2-2 and later)

• Storage engine: Speedb only
• RAM management: Automatic. Redis manages RAM allocation internally.
• Configuration: rofRamSize isn't validated with minimum ratio requirements.
• Redis versions: Redis 8.0 and later

Auto Tiering ( 7.22.2-22 and earlier)

• Storage engine: RocksDB or Speedb
• RAM management: Manual. Requires explicit rofRamSize configuration.
• Validation: rofRamSize must be at least 10% of memorySize and can't exceed memorySize.
• Redis versions: Redis versions earlier than 8.0

The operator doesn't support Redis 7.4 preview for Redis Flex. Redis 7.4 databases use Auto Tiering regardless of cluster policy. To use Redis Flex, upgrade to Redis 8.0 or later.

Prerequisites

Before you create your Redis clusters or databases, ensure that your SSDs meet the following requirements:

• Locally attached to worker nodes in your Kubernetes cluster
• Formatted and mounted on the nodes that run Redis Enterprise pods
• Dedicated to Redis Flex and not shared with other parts of the database (for example, durability or binaries)
• Provisioned as local persistent volumes
  • You can use a local volume provisioner to provision volumes dynamically.
• Configured with a StorageClass resource that has a unique name

For more information about node storage, see [Node persistent and ephemeral storage]({{< relref "/operate/rs/installing-upgrading/install/plan-deployment/persistent-ephemeral-storage" >}}).

Create a Redis Enterprise cluster

To deploy a Redis Enterprise cluster (REC) with Redis Flex, specify the following fields in the redisOnFlashSpec section of your [REC custom resource]({{< relref "/operate/kubernetes/reference/api/redis_enterprise_cluster_api#specredisonflashspec" >}}):

• enabled: true - Enables Redis Flex
• bigStoreDriver: speedb - Sets the flash storage driver
• storageClassName - Specifies the storage class name
• flashDiskSize - Sets the minimum flash disk size

{{<warning>}} Redis Flex doesn't support PVC expansion. Do not enable enablePersistentVolumeResize in the REC persistentSpec if you use redisOnFlashSpec. Enabling both will cause conflicts. {{</warning>}}

The following example shows a Redis Enterprise cluster custom resource with these fields:

apiVersion: app.redislabs.com/v1
kind: RedisEnterpriseCluster
metadata:
  name: "rec"
  labels:
    app: redis-enterprise
spec:
  nodes: 3
  redisOnFlashSpec:
    enabled: true
    bigStoreDriver: speedb        # Only 'speedb' is suitable for Redis Flex
    storageClassName: local-scsi
    flashDiskSize: 100G

{{<note>}}

• Set the enabled field to true.
• Use bigStoreDriver: speedb for Redis Flex support on Redis 8.0 and later.
• The flashStorageEngine field is deprecated. Use bigStoreDriver instead.

{{</note>}}

Create a Redis Enterprise database

By default, new databases use RAM only. To create a Redis Enterprise database (REDB) that uses Redis Flex and takes advantage of locally attached SSDs, set isRof to true.

Specify the following fields in the REDB custom resource:

• isRof: true - Enables Redis Flex
• redisVersion - Set to "8.0" or later
• memorySize - Defines the total combined memory size (RAM + flash)
• rofRamSize - (Optional) Defines the RAM capacity for the database

The following example shows a REDB custom resource:

apiVersion: app.redislabs.com/v1alpha1
kind: RedisEnterpriseDatabase
metadata:
  name: redis-flex-db
spec:
  redisEnterpriseCluster:
    name: rec
  isRof: true
  redisVersion: "8.0"
  memorySize: 2GB
  rofRamSize: 0.5GB

{{< note >}} Redis Flex automatically manages RAM allocation. You can specify rofRamSize, but it isn't subject to the 10% minimum ratio requirement that applies to Auto Tiering. The operator doesn't validate or enforce minimum RAM ratios for Redis 8.0 and later databases. {{< /note >}}

Upgrade from Auto Tiering to Redis Flex

When you upgrade a database from a Redis version earlier than 8.0 to Redis 8.0 or later, Redis Server automatically migrates the database from Auto Tiering to Redis Flex. The operator detects this migration and makes the following changes:

1. Stops validating the rofRamSize ratio requirement.
2. Stops reconciling the bigstore_ram_size field to avoid configuration drift.
3. Continues to preserve the database configuration.

Example upgrade scenario

The following example shows how to upgrade a database from Auto Tiering to Redis Flex:

1. Create a database on Redis 7.2 with rofRamSize: 200MB.
2. Upgrade the database to Redis 8.0 by updating spec.redisVersion to "8.0".
3. Redis Server automatically converts the database to Redis Flex.
4. The operator detects the conversion and adapts its reconciliation behavior.
5. Redis now manages the rofRamSize field automatically. You can keep the field in the spec for backward compatibility.