Re: Is scrubbing md-aware in any way?

[Mariusz Mazur <mariusz.g.mazur@gmail.com>]

niedz., 25 wrz 2022 o 20:46 Neal Gompa <ngompa13@gmail.com> napisał(a):
>
> On Wed, Sep 14, 2022 at 10:37 AM David Sterba <dsterba@suse.cz> wrote:
> >
> > On Tue, Sep 13, 2022 at 04:15:26PM +0200, Mariusz Mazur wrote:
> > > Hi, it's my understanding that when running a scrub on a btrfs raid,
> > > if data corruption is detected, the process will check copies on other
> > > devices and heal the data if possible.
> > >
> > > Is any of that functionality available when running on top of an md
> > > raid?
> >
> > No, the type of block device under btrfs is considered the same in all
> > cases, except zoned devices, so any advanced information exchange or
> > control like devices reporting bad sectors or btrfs asking to repair the
> > underlying device by its own means.
> >
> > > When a scrub notices an issue, does it have any mechanism of
> > > telling md "hey, there's a problem with these sectors" and working
> > > with it to do something about that or is it all up to the admin to
> > > deal with the "file corrupted" message?
> >
> > It's up to the admin. I've looked if there's some API outside of the
> > md-raid implementation, but there's none so it would have to be created
> > first in for the btrfs <-> md cooperation.
>
> IIRC, the Synology folks created such an API for their own use-case.
> Does anyone on-list know the folks at Synology to see if they'd be
> interested in working with us and the md folks to make this fully
> supported upstream?
>
>
> --
> 真実はいつも一つ！/ Always, there's only one truth!

Yes, wondering how synology uses btrfs on top of md raid effectively
is what prompted my question. I'd like to be able to use btrfs (and
other filesystems) in such a fashion as well.