On Fri, 11 Nov 2022 14:05:33 -0500 Dan Ritter <d...@randomstring.org> wrote:
> Claimed MTBF: 1 million hours. Believe it or not, this is par > for the course for high-end disks. > > 24 hours a day, 365 days a year: 8760 hours per year. > 1000000/8760 = 114 years. > > So, no: MTBF numbers must be presumed to be malicious lies. With your interpretation every single drive would not be allowed to fail before its MTBF value. That's wrong. MTBF is a mean value for all drives of this type, not a guaranteed minimum value for a single drive. If there are one million drives, statistically with every hour one drive will fail. That means, even with correctly claiming an MTBF of 1 million hours, one of those million drives will statistically(!) run only one hour before it fails. Some more practical explanation: If you have one thousand drives then you have to expect one drive failure for every one thousand hours (MTBF=1,000,000). Statistically you have to expect nearly nine of those drives to fail per year (if I did my math correctly). With higher MTBF values this value will be smaller, with lower MTBF values you'd have to expect more drives to fail. But this is only a pure statistical value. If you are the one of a million, your single drive will fail within the first hour... (and on top there are other details, like: the MTBF is calculated for specific environmental conditions; if your environment is more rogue, then you'd have to expect a lower MTBF than the one declared by the vendor... and vice versa) regards hede
