[dm-devel] Re: Is there a grand plan for FC failover?

[Philip R. Auld]

Rumor has it that on Wed, Jan 28, 2004 at 05:16:51PM -0500 James Bottomley said:
> On Wed, 2004-01-28 at 16:02, Smart, James wrote:
> > I'd add one additional issue :
> > 
> > 3) SCSI Reservations
> > 
> > I guess this could be considered a part of (2), but given that reservations
> > bring in a host of additional problems, and potentially brings up multi-host
> > configs/clusters as well...
> 
> The current crop of cluster implementations that use reservations manage
> quite well in user space alone.  Certainly, though, the presence of
> reservations can interfere with failover code and may be considered a
> problem that needs to be solved in multi-path...it all depends on how
> the multi-path devices react to path switching in the face of
> reservations.
> 

It needs to be known to the pathing layer if you've got load balancing. 
It has to know which path has the reservation and only use that one.
 
> I'm open to suggestions on this,  but I think it should be done
> separately as part of a device ownership API.
> 
> James
> 

-- 
Philip R. Auld, Ph.D.  	        	       Egenera, Inc.    
Principal Software Engineer                   165 Forest St.
(508) 858-2628                            Marlboro, MA 01752