Scrub incredibly slow with 13.0-RC3 (as well as RC1 & 2)

[Mathieu Chouquet-Stringer]

On Tue, Mar 23, 2021 at 01:27:00AM +0100, Mathieu Chouquet-Stringer wrote:
>   scan: scrub in progress since Tue Mar 23 01:03:09 2021
>         63.0G scanned at 87.5M/s, 63.0G issued at 87.5M/s, 24.5T total
>         0B repaired, 0.25% done, 3 days 09:14:15 to go
> 
> I'll let it run overnight and I'll check back tomorrow: I mean you
> can't trust the progress bar...

So it's better but still not great, it's been running for 9.5 hours now:

  scan: scrub in progress since Tue Mar 23 01:03:09 2021
        3.90T scanned at 121M/s, 3.90T issued at 121M/s, 24.5T total
        0B repaired, 15.93% done, 2 days 01:24:58 to go

For reference I had the following after 12 hours with the new scrub algorithm:

  scan: scrub in progress since Sun Mar 21 23:47:40 2021
        2.82T scanned at 77.8M/s, 2.24T issued at 62.0M/s, 24.5T total
        0B repaired, 9.17% done, 4 days 08:23:32 to go
-- 
Mathieu Chouquet-Stringer
            The sun itself sees not till heaven clears.
	             -- William Shakespeare --