{
  "id": "auto-tiering",
  "title": "Auto Tiering Metrics",
  "url": "https://redis.io/docs/latest/operate/rs/7.8/references/metrics/auto-tiering/",
  "summary": "",
  "content": "\nThese metrics are additional metrics for [Auto Tiering ]() databases.\n\n#### % Values in RAM\n\nPercent of keys whose values are stored in RAM.\n\nA 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.\n\nIf the percent of values in RAM is low for a subset of the database's shards, it might also indicate an unbalanced database.\n\n**Components measured**: Database and Shard\n\n#### Values in flash\n\nNumber of keys with values stored in flash, not including [replication]().\n\n**Components measured**: Database and Shard\n\n#### Values in RAM\n\nNumber of keys with values stored in RAM, not including [replication]().\n\n**Components measured**: Database and Shard \n\n#### Flash key-value operations\n\nNumber of operations on flash key values (read + write + del) per second.\n\n**Components measured**: Node\n\n#### Flash bytes/sec\n\nNumber of total bytes read and written per second on flash memory.\n\n**Components measured**: Cluster, Node, Database, and Shard\n\n#### Flash I/O operations/sec\n\nNumber of input/output operations per second on the flash storage device.\n\n**Components measured**: Cluster and Node\n\n#### RAM:Flash access ratio\n\nRatio between logical Redis key value operations and actual flash key value operations.\n\n**Components measured**: Database and Shard\n\n#### RAM hit ratio\n\nRatio of requests processed directly from RAM to total number of requests processed.\n\n**Components measured**: Database and Shard\n\n#### Used flash\n\nTotal amount of memory used to store values in flash.\n\n**Components measured**: Database and Shard\n\n#### Free flash\n\nAmount of free space on flash storage. \n\n**Components measured**: Cluster and Node\n\n#### Flash fragmentation\n\nRatio between the used logical flash memory and the physical flash memory that is used.\n\n**Components measured**: Database and Shard\n\n#### Used RAM\n\nTotal size of data stored in RAM, including keys, values, overheads, and [replication]() (if enabled).\n\n**Components measured**: Database and Shard\n\n#### RAM dataset overhead\n\nPercentage of the [RAM limit](#ram-limit) that is used for anything other than values, such as key names, dictionaries, and other overheads.\n\n**Components measured**: Database and Shard\n\n#### RAM limit\n\nMaximum amount of RAM that can be used in bytes.\n\n**Components measured**: Database\n\n#### RAM usage\n\nPercentage of the [RAM limit](#ram-limit) used.\n\n**Components measured**: Database\n\n#### Storage engine usage\n\nTotal count of shards used, filtered by the sorage engine (Speedb / RockSB) per given database.\n\n**Components measured**: Database, Shards\n\n\n\n#### Calculated metrics\n\nThese RoF statistics can be calculated from other metrics.\n\n- RoF average key size with overhead\n\n    ([ram_dataset_overhead](#ram-dataset-overhead) * [used_ram](#used-ram))\n                    / ([total_keys]() * 2)\n\n- RoF average value size in RAM\n\n    ((1 - [ram_dataset_overhead](#ram-dataset-overhead)) * [used_ram](#used-ram)) / ([values_in_ram](#values-in-ram) * 2)\n\n- RoF average value size in flash\n\n    [used_flash](#used-flash) / [values_in_flash](#values-in-flash)    \n",
  "tags": ["docs","operate","rs"],
  "last_updated": "2026-04-01T08:10:08-05:00"
}