Re: Problem with file system

["Austin S. Hemmelgarn" <ahferroin7@gmail.com>]

On 2017-11-07 23:50, Chris Murphy wrote:
> On Tue, Nov 7, 2017 at 6:02 AM, Austin S. Hemmelgarn
> <ahferroin7@gmail.com> wrote:
> 
>> * Optional automatic correction of errors detected during normal usage.
>> Right now, you have to run a scrub to correct errors. Such a design makes
>> sense with MD and LVM, where you don't know which copy is correct, but BTRFS
>> does know which copy is correct (or how to rebuild the correct data), and it
>> therefore makes sense to have an option to automatically rebuild data that
>> is detected to be incorrect.
> 
> ?
> 
> It definitely does fix ups during normal operations. During reads, if
> there's a UNC or there's corruption detected, Btrfs gets the good
> copy, and does a (I think it's an overwrite, not COW) fixup. Fixups
> don't just happen with scrubbing. Even raid56 supports these kinds of
> passive fixups back to disk.
I could have sworn it didn't rewrite the data on-disk during normal 
usage.  I mean, I know for certain that it will return the correct data 
to userspace if at all possible, but I was under the impression it will 
just log the error during normal operation.