Re: [PATCH] md/raid10: prioritize adding disk to 'removed' mirror

[Li Nan]

在 2023/5/29 21:00, Yu Kuai 写道:
> Hi,
>
> 在 2023/05/27 17:20, linan666@xxxxxxxxxxxxxxx 写道:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > When add a new disk to raid10, it will traverse conf->mirror from start
> > and find one of the following mirror to add:
> >    1. mirror->rdev is set to WantReplacement and it have no replacement,
> >       set new disk to mirror->replacement.
> >    2. no mirror->rdev, set new disk to mirror->rdev.
> >
> > There is a array as below (sda is set to WantReplacement):
> >
> >      Number   Major   Minor   RaidDevice State
> >         0       8        0        0      active sync set-A   /dev/sda
> >         -       0        0        1      removed
> >         2       8       32        2      active sync set-A   /dev/sdc
> >         3       8       48        3      active sync set-B   /dev/sdd
> >
> > Use 'mdadm --add' to add a new disk to this array, the new disk will
> > become sda's replacement instead of add to removed position, which is
> > confusing for users. Meanwhile, after new disk recovery success, sda
> > will be set to Faulty.
> >
> > Prioritize adding disk to 'removed' mirror is a better choice. In the
> > above scenario, the behavior is the same as before, except sda will not
> > be deleted. Before other disks are added, continued use sda is more
> > reliable.
>
> I think this change make sense, however, it's better to do this for all
> personality instead of just for raid10.
>
> Thanks,
> Kuai

raid5 is currently like this. If others are OK with this changes to 
raid10, I will modify raid1 later.

--
Thanks,
Nan