[dm-devel] Re: raid failure and LVM volume group availability

[Neil Brown]

On Tuesday May 26, goswin-v-b at web.de wrote:
> hank peng <pengxihan at gmail.com> writes:
> 
> > Only one of disks in this RAID1failed, it should continue to work with
> > degraded state.
> > Why LVM complained with I/O errors??
> 
> That is because the last drive in a raid1 can not fail:
> 
> md9 : active raid1 ram1[1] ram0[2](F)
>       65472 blocks [2/1] [_U]
> 
> # mdadm --fail /dev/md9 /dev/ram1
> mdadm: set /dev/ram1 faulty in /dev/md9
> 
> md9 : active raid1 ram1[1] ram0[2](F)
>       65472 blocks [2/1] [_U]
> 
> See, still marked working.
> 
> MfG
>         Goswin
> 
> PS: Why doesn't mdadm or kernel give a message about not failing?

-ENOPATCH :-)

You would want to rate limit any such message from the kernel, but it
might make sense to have it.

NeilBrown