This[1] page explains MTTF as follows: The MTTF is a statistical value that defines after how much time a first failure in a population of devices may occur (m

This[1] page explains MTTF as follows: The MTTF is a statistical value that defines after how much time a first failure in a population of devices may occur (measured in hours). If MTTF is given as 1 million hours, and the drives are operated within the specifications, one drive failure per hour can be expected for a population of 1 million drives. For the more realistic quantity of 1000 drives, a Managed Service Provider (MSP) should plan for a failure every 1000 hours (almost 42 days). It also has some formulas to convert MTTF to Annualized Failure Rate (AFR). [1]: https://www.toshiba-storage.com/trends-technology/mttf-what-hard-drive-reliability-really-means/ https://www.toshiba-storage.com/trends-technology/mttf-what-...