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Re:Bcachefs may be headed out of the kernel by ars on Friday July 04, 2025 @04:54PM (#44467818)
> The likelihood .. of this occurring

That's 10^14 bits for a consumer drive. That's just 12TB. A heavy user (lots of videos or games) would see a bit flip a couple times a year.

Re:Bcachefs may be headed out of the kernel by magicalhippo on Friday July 04, 2025 @06:01PM (#44468204)
I do monthly scrubs on my NAS, I have 8 14-20TB drives that are quite full.

According to that 10^14 metric I should see read errors just about every month. Except I have just about zero.

Current disks are ~4 years, runs 24/7, and excluding a bad cable incident I've had a single case of a read error (recoverable, thanks ZFS).

I suspect those URE numbers are made by the manufacturers figuring out they can be sure the disk will do 10^14, but they don't actually try to find the real number because 10^14 is good enough.

Re:Bcachefs may be headed out of the kernel by ars on Friday July 04, 2025 @08:38PM (#44469199)
If you are using enterprise drives those are 10^16, so that might explain it.
Re:Bcachefs may be headed out of the kernel by magicalhippo on Friday July 04, 2025 @09:08PM (#44469334)
Fair, newest ones are, but two of my older current drives are IronWolfs 16TB which are 10^15 in the specs[1], and they've been running for 5.4 years. Again without any read errors, monthly scrubs, and of course daily use.

And before that I have been using 8x WD Reds 3TB for 6-7 years, which have 10^14 in the specs[2], and had the same experience with those.

Yes smaller size, but I ran scrubbing on those biweekly, and over so many years?

[1]: https://www.seagate.com/files/www-content/datasheets/pdfs/ir...

[2]: https://documents.westerndigital.com/content/dam/doc-library...

Re:Bcachefs may be headed out of the kernel by ryao on Saturday July 05, 2025 @02:15PM (#44474491)
> I suspect those URE numbers are made by the manufacturers figuring out they can be sure the disk will do 10^14, but they don't actually try to find the real number because 10^14 is good enough.

I am inclined to agree. However, I have one thought to the contrary. When a mechanical drive is failing, you tend to have debris inside the drive hitting the platters, causing damage that creates more debris, accelerating the drive’s eventual death, with read errors becoming increasingly common while it happens. When those are included in averages, the 10^14 might very well be accurate. I have not done any rigorous analysis to justify this thought and I do not have the data to be able to do that analysis. It is just something that occurs to me that might justify the 10^14 figure.

Re:Bcachefs may be headed out of the kernel by Dylan16807 on Friday July 04, 2025 @09:16PM (#44469358)
I'm not really sure how you're supposed to interpret those error rates. The average read error probably has a lot more than 1 flipped bit, right? And if the average error affects 50 bits, then you'd expect 50x fewer errors? But I have no idea what the actual histogram looks like.
Re:Bcachefs may be headed out of the kernel by timewizard on Friday July 04, 2025 @10:31PM (#44469681)
Is that raw error rate or uncorrected error rate?