Re: Fault tolerance with badblocks

[Wols Lists <antlists@youngman.org.uk>]

On 09/05/17 17:05, Chris Murphy wrote:
>> Yes you have saved a sector sparing. Note that a consumer 3TB drive can
>> > return, on average, one error every time it's read from end to end 3 times,
>> > and still be considered "within spec" ie "not faulty" by the manufacturer.

> All specs say "less than" which means it's a maximum permissible rate,
> not an average. We have no idea what the minimum error rate is - we
> being consumers. It's possible high volume users (e.g. Backblaze) have
> data on this by now.
> 
In other words, an error rate that high is "acceptable".

And to design software that quite explicitly expects greater perfection
than the hardware itself is guaranteed to provide is, in my humble
opinion, downright negligent!!!

I'm sorry, but like Linus, I take an *engineering* approach to this
stuff, not a mathematical approach. In a mathematical world everything
works perfectly. In an engineering world, things go wrong. You should
always plan for the worst case. But to fail to plan for "the worst
*acceptable* case" is just plain IDIOTIC.

Cheers,
Wol