Has anyone seen an HDD with bit error rate lower than 10^-15 ?

I've looked at latest WD Red Pros and WD Ultrastars and they all have bit error rate 10^15, even though they're like 10TB = 10^13 * 8 =~ 10^14 bits big...

so like, 10% chance a RAID rebuild will fail? That's huge...

@lanodan are they error-correcting codes, or just error-detecting?

@lanodan well those can only turn a silent data corruption into an unrecoverable read error.

I already have an unrecoverable read error (HDDs have built-in per-sector checksums).

If you have a fully operational RAID1, and you encounter an URE, you just read the value of that sector from the other disk and overwrite the faulty one, hoping the HDD will reallocate it.

But that requires (1) stumbling upon that URE while you still have a non-degraded array, and (2) HDD correctly reallocating


@wolf480pl @lanodan ZFS provides periodic scrubs for that case, going over all written data and verifying the checksums to correct the errors on the data that has not been read recently (which would get auto-corrected then).

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@mbernabe @lanodan so a partol read? Yeah I said lower kn the thread that id'd probably help

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