Re: read and write back full disk to trigger relocation

On 5/30/23 16:49, Sysadmin Lists wrote:
> David Christensen May 30, 2023, 4:16:09 PM
>> I would say the experiment should be repeated on real HDD's, but how do
>> I detect if identical data has being written to the platters?  The HDD
>> controller also has a cache and could optimize away such writes.
> 
> Isn't that what dd is claiming authoritatively to be doing? Otherwise, putting
> that example in the manpage is dangerous and can lead to unexpected data loss.
> 
> I don't speak C++ very good, but here's the source:
> https://github.com/coreutils/coreutils/blob/master/src/dd.c

<snip>


Looking at FreeBSD code will not provide information about the HDD 
controller hardware and firmware.


David