| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-C61 | ESP32-H2 | ESP32-H21 | ESP32-H4 | ESP32-P4 | ESP32-S2 | ESP32-S3 | | ----------------- | ----- | -------- | -------- | -------- | -------- | --------- | -------- | --------- | -------- | -------- | -------- | -------- | # Non-Volatile Storage (NVS) Statistics Example This example demonstrates the usage of obtaining and interpreting statistics about the a given NVS partition, namely free/used/available/total entries and namespace count. The default "nvs" partition is first erased, then a mock string data configuration is written to 2 different namespaces, followed by checking the changed statistics and mainly the number of newly used NVS entries. Statistics obtained via [nvs_get_stats()](https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/storage/nvs_flash.html#_CPPv413nvs_get_statsPKcP11nvs_stats_t) are the following: | | | | -------------- | ------------------- | | `available entries` | Essential statistic, specifies free non-reserved entries available for data storage. | | `used entries` | Includes 1 overhead entry per namespace + actual data entries used by data storage. | | `free entries` | Free entries are both the free available to the user entries, and free but internally reserved (not available to the user). | | `total entries` | Number of all entries (free + used). | Detailed functional description of NVS and API is provided in [documentation](https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/storage/nvs_flash.html). ## How to use example ### Hardware required This example does not require any special hardware, and can be run on any common development board. ### Build and flash Build the project and flash it to the board, then run monitor tool to view serial output: ``` idf.py -p PORT flash monitor ``` (To exit the serial monitor, type ``Ctrl-]``.) See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects. ## Example Output ``` ... I (265) nvs_statistics_example: Erasing the contents of the default NVS partition... I (475) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_data'... I (485) nvs_statistics_example: Getting NVS statistics... I (485) nvs_statistics_example: NVS statistics: I (485) nvs_statistics_example: Used NVS entries: 1 I (485) nvs_statistics_example: Free NVS entries: 755 I (495) nvs_statistics_example: Available NVS entries: 629 I (495) nvs_statistics_example: Total NVS entries: 756 I (505) nvs_statistics_example: Namespace count: 1 I (505) nvs_statistics_example: Writing mock data key-value pairs to NVS namespace '_mock_data'... I (525) nvs_statistics_example: Committing data in NVS namespace '_mock_data'... I (525) nvs_statistics_example: Getting post-commit NVS statistics... I (525) nvs_statistics_example: NVS statistics: I (535) nvs_statistics_example: Used NVS entries: 30 I (535) nvs_statistics_example: Free NVS entries: 726 I (545) nvs_statistics_example: Available NVS entries: 600 I (545) nvs_statistics_example: Total NVS entries: 756 I (555) nvs_statistics_example: Namespace count: 1 I (555) nvs_statistics_example: Newly used entries match expectation. I (565) nvs_statistics_example: Newly used entries: 29, expected: 29. I (575) nvs_statistics_example: NVS handle for namespace '_mock_data' closed. I (575) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_data'... I (585) nvs_statistics_example: Reading stored data from NVS namespace '_mock_data'... I (595) nvs_statistics_example: Read key-value pair from NVS: 'wifi_ssid':'HomeNetwork' I (605) nvs_statistics_example: Read key-value pair from NVS: 'wifi_pass':'MySecretPass' I (605) nvs_statistics_example: Read key-value pair from NVS: 'dev_name':'LivingRoomThermostat' I (615) nvs_statistics_example: Read key-value pair from NVS: 'temp_unit':'Celsius' I (625) nvs_statistics_example: Read key-value pair from NVS: 'target_temp':'22' I (635) nvs_statistics_example: Read key-value pair from NVS: 'eco_mode':'false' I (635) nvs_statistics_example: Read key-value pair from NVS: 'fw_version':'1.2.3' I (645) nvs_statistics_example: Read key-value pair from NVS: 'led_bright':'80' I (655) nvs_statistics_example: Read key-value pair from NVS: 'auto_update':'true' I (665) nvs_statistics_example: Read key-value pair from NVS: 'last_sync':'2025-01-01T08:00:00Z' I (665) nvs_statistics_example: Read key-value pair from NVS: 'user_lang':'en' I (675) nvs_statistics_example: Read key-value pair from NVS: 'long_token':'2f8c1e7b5a4d9c6e3b0f1a8e5d7c2b6f4e1a9c7b' I (685) nvs_statistics_example: Read key-value pair from NVS: 'very_long_token':'7e2b1c9f5a4d8e3b0f1a6c7e2d9b5a4c8e1f7b2d6c3a9e5b0f1a8c7e2d9b5a4c8e1f7b2d6c3a9e5b' I (705) nvs_statistics_example: NVS handle for namespace '_mock_data' closed. I (705) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_backup'... I (715) nvs_statistics_example: Getting NVS statistics... I (725) nvs_statistics_example: NVS statistics: I (725) nvs_statistics_example: Used NVS entries: 31 I (735) nvs_statistics_example: Free NVS entries: 725 I (735) nvs_statistics_example: Available NVS entries: 599 I (745) nvs_statistics_example: Total NVS entries: 756 I (745) nvs_statistics_example: Namespace count: 2 I (755) nvs_statistics_example: Writing mock data key-value pairs to NVS namespace '_mock_backup'... I (765) nvs_statistics_example: Committing data in NVS namespace '_mock_backup'... I (765) nvs_statistics_example: Getting post-commit NVS statistics... I (775) nvs_statistics_example: NVS statistics: I (775) nvs_statistics_example: Used NVS entries: 60 I (785) nvs_statistics_example: Free NVS entries: 696 I (785) nvs_statistics_example: Available NVS entries: 570 I (795) nvs_statistics_example: Total NVS entries: 756 I (795) nvs_statistics_example: Namespace count: 2 I (805) nvs_statistics_example: Newly used entries match expectation. I (805) nvs_statistics_example: Newly used entries: 29, expected: 29. I (815) nvs_statistics_example: NVS handle for namespace '_mock_backup' closed. I (825) nvs_statistics_example: Opening Non-Volatile Storage (NVS) handle for namespace '_mock_backup'... I (835) nvs_statistics_example: Reading stored data from NVS namespace '_mock_backup'... I (835) nvs_statistics_example: Read key-value pair from NVS: 'wifi_ssid':'HomeNetwork' I (845) nvs_statistics_example: Read key-value pair from NVS: 'wifi_pass':'MySecretPass' I (855) nvs_statistics_example: Read key-value pair from NVS: 'dev_name':'LivingRoomThermostat' I (865) nvs_statistics_example: Read key-value pair from NVS: 'temp_unit':'Celsius' I (865) nvs_statistics_example: Read key-value pair from NVS: 'target_temp':'22' I (875) nvs_statistics_example: Read key-value pair from NVS: 'eco_mode':'false' I (885) nvs_statistics_example: Read key-value pair from NVS: 'fw_version':'1.2.3' I (895) nvs_statistics_example: Read key-value pair from NVS: 'led_bright':'80' I (895) nvs_statistics_example: Read key-value pair from NVS: 'auto_update':'true' I (905) nvs_statistics_example: Read key-value pair from NVS: 'last_sync':'2025-01-01T08:00:00Z' I (915) nvs_statistics_example: Read key-value pair from NVS: 'user_lang':'en' I (925) nvs_statistics_example: Read key-value pair from NVS: 'long_token':'2f8c1e7b5a4d9c6e3b0f1a8e5d7c2b6f4e1a9c7b' I (935) nvs_statistics_example: Read key-value pair from NVS: 'very_long_token':'7e2b1c9f5a4d8e3b0f1a6c7e2d9b5a4c8e1f7b2d6c3a9e5b0f1a8c7e2d9b5a4c8e1f7b2d6c3a9e5b' I (945) nvs_statistics_example: NVS handle for namespace '_mock_backup' closed. I (955) nvs_statistics_example: Returning from app_main(). I (955) main_task: Returned from app_main() ... ```