Re: [RFC] Multi-path IO in 2.5/2.6 ?

Patrick Mochel
2002-09-10T19:00:47Z

On Tue, 10 Sep 2002, Patrick Mansfield wrote:

> On Tue, Sep 10, 2002 at 10:21:53AM -0700, Patrick Mochel wrote:
> >
> > > > > Generic device naming consistency is a problem if multiple devices
> > > > > show up with the same id.
> > > >
> > > > Patrick Mochel has an open task to come up with a solution to this.
> > >
> > > I don't think this can be solved if multiple devices show up with the same
> > > id. If I have five disks that all say I'm disk X, how can there be one
> > > name or handle for it from user level?
> >
> > Easy: you map the unique identifier of the device to a name in userspace.
> > In our utopian future, /sbin/hotplug is called with that unique ID as one
> > of its parameters. It searches for, and finds names based on the ID is. If
> > the name(s) already exist, then it doesn't continue.
> >
> >
> > -pat
>
> But then if the md or volume manager wants to do multi-path IO it
> will not be able to find all of the names in userspace since the
> extra ones (second path and on) have been dropped.

Which is it that you want? One canonical name or all the paths? I supplied
a solution for the former in my repsonse. The latter is solved via the
exposure of the paths in driverfs, which has been discussed previously.

-pat