# Redis Flex and Auto Tiering Metrics

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The following additional metrics for [Redis Flex and Auto Tiering ](https://redis.io/docs/latest/operate/rs/databases/flash) databases are available in the Redis Software Cluster Manager UI.

![images/rs/screenshots/metrics/flash-db-metrics.png](https://redis.io/docs/latest/images/rs/screenshots/metrics/flash-db-metrics.png)

#### % Values in RAM

Percent of keys whose values are stored in RAM.

A low percentage alert means most of the RAM is used for holding keys and not much RAM is available for values. This can be due to a high number of small keys or a few large keys. Inserting more keys might cause the database to run out of memory.

If the percent of values in RAM is low for a subset of the database's shards, it might also indicate an unbalanced database.

**Components measured**: Database and Shard

#### Values in flash

Number of keys with values stored in flash, not including [replication](https://redis.io/docs/latest/operate/rs/databases/durability-ha/replication).

**Components measured**: Database and Shard

#### Values in RAM

Number of keys with values stored in RAM, not including [replication](https://redis.io/docs/latest/operate/rs/databases/durability-ha/replication).

**Components measured**: Database and Shard 

#### Flash key-value operations

Number of operations on flash key values (read + write + del) per second.

**Components measured**: Node

#### Flash bytes/sec

Number of total bytes read and written per second on flash memory.

**Components measured**: Cluster, Node, Database, and Shard

#### Flash I/O operations/sec

Number of input/output operations per second on the flash storage device.

**Components measured**: Cluster and Node

#### RAM:Flash access ratio

Ratio between logical Redis key value operations and actual flash key value operations.

**Components measured**: Database and Shard

#### RAM hit ratio

Ratio of requests processed directly from RAM to total number of requests processed.

**Components measured**: Database and Shard

#### Used flash

Total amount of memory used to store values in flash.

**Components measured**: Database and Shard

#### Free flash

Amount of free space on flash storage. 

**Components measured**: Cluster and Node

#### Flash fragmentation

Ratio between the used logical flash memory and the physical flash memory that is used.

**Components measured**: Database and Shard

#### Used RAM

Total size of data stored in RAM, including keys, values, overheads, and [replication](https://redis.io/docs/latest/operate/rs/databases/durability-ha/replication) (if enabled).

**Components measured**: Database and Shard

#### RAM dataset overhead

Percentage of the [RAM limit](#ram-limit) that is used for anything other than values, such as key names, dictionaries, and other overheads.

**Components measured**: Database and Shard

#### RAM limit

Maximum amount of RAM that can be used in bytes.

**Components measured**: Database

#### RAM usage

Percentage of the [RAM limit](#ram-limit) used.

**Components measured**: Database

#### Storage engine usage

Total count of shards used, filtered by the sorage engine (Speedb / RockSB) per given database.

**Components measured**: Database, Shards



#### Calculated metrics

These RoF statistics can be calculated from other metrics.

- RoF average key size with overhead

    ([ram_dataset_overhead](#ram-dataset-overhead) * [used_ram](#used-ram))
                    / ([total_keys](https://redis.io/docs/latest/operate/rs/references/metrics/database-operations#total-keys) * 2)

- RoF average value size in RAM

    ((1 - [ram_dataset_overhead](#ram-dataset-overhead)) * [used_ram](#used-ram)) / ([values_in_ram](#values-in-ram) * 2)

- RoF average value size in flash

    [used_flash](#used-flash) / [values_in_flash](#values-in-flash)