[dm-devel] [QUESTION]: multipath device with wrong path lead to metadata err

[Martin Wilck]

On Wed, 2021-01-20 at 07:02 -0600, Roger Heflin wrote:
> 
> 
> I don't know if this helps, or is exactly like what he is
> duplicating:
> 
> I debugged and verified a corruption issue a few years ago where this
> was what happened:
> 
> DiskA was presented at say sdh (via SAN) and a multipath device was
> created on top of its paths, then diskA was unpresented and new disks
> were put back in the same zone.
> DiskB was now presented in the same slot (zone+lunid/sdh) and
> inherited by the still in place multipath device/mapping.    In this
> case I don't believe there was ever a device level event for sdh.

If there really was no event, what should multipathd have done? We
can't poll SCSI devices for device ID changes. Even if we did, how
often should we do it? A wrong disk in an array might lead to data
corruption in the course of just a few ms.

Anyway, if this was a few years ago, I'm confident that we do better in
this area today than we used to, even if lixiaokeng's case shows that
we still have dark areas.

Regards
Martin