James (no.delete@this.thanks.invalid) on May 6, 2021 2:36 am wrote:
> Etienne Lorrain (etienne_lorrain.delete@this.yahoo.fr) on May 6, 2021 1:08 am wrote:
>
> > I do not think there is any advantage in an "ECC line size" bigger than a very few hundred bytes (and
> > there is disadvantages like latency)
>
> That was one of the big advantages Western Digital claimed back when 4K disk blocks were first being introduced:

The
> principle (sic) problem here is that ECC correction takes place in 512B chunks, while ECC can be more efficient
> when used over larger chunks of data. If ECC data is calculated against a larger sector, even though more ECC
> data is necessary than for a single 512B sector, less ECC data than the sum of multiple sectors is needed to
> maintain the same level of operational reliability. One estimate for 4K sector technology puts this at 100 bytes
> of ECC data needed for a 4K sector, versus 320 (40x8) for 8 512B sectors. Furthermore the larger sectors means
> that larger erroneous chunks of data can be corrected (burst error correction), something that was becoming harder
> as greater areal densities made it easier to wipe out larger parts of a 512B sector.


I don't know enough about modern hard disk track formats, but historically, inter-block-gaps tended to scale more poorly than bits. IOW, if you doubled the linear bit density, you'd typically see less than a halving of the IBG, leading to more and more of the track being dedicated to IBGs. Going to a larger block size would help on that front too. If nothing else, the replacement of eight IBGs with one would be beneficial.