https://www.backblaze.com/blog/hard-drive-stats-for-q1-2018/

Lifetime Hard Drive Reliability Statistics
While the quarterly chart presented earlier gets a lot of interest, the real test of any drive model is over time. Below is the lifetime failure rate chart for all the hard drive models which have 45 or more drives in operation as of March 31st, 2018. For each model, we compute their reliability starting from when they were first installed.

Bei externen Gehäusen kannst zusätzlich noch auf individuelle Faktoren achten, wie z.B. hat das Gehäuse einen Netzschalter.