On Thu, 2011-07-28 at 13:57 -0700, Roland Dreier wrote: > > My initial thought is that in a multi-path situation, as above, we get > > two enclosures appearing as well (one down each path). If we > > incorporated the idea of topological subtrees into the identity matching > > code, we'd end up filling each of the enclosures with the path connected > > devices. That seems to be an easy situation for multi-path drivers to > > sort out and one requiring no alteration of the existing enclosure code > > (except to do the topological subtree search). > > Ah, good insight: we do have two copies of the expander device, and so > it would be natural to attach each disk to the expander device on the > same path to that disk. > > I'm a bit confused by what you mean about multi-path drivers though -- > it would seem we would need the enclosure stuff to handle this > somehow? It seems that if I have this situation, my HBA driver (eg > mpt2sas) will discover the SCSI bus, hit an enclosure, trigger loading > the ses driver (which pulls in the enclosure driver), and then > continue discovering disks. And it seems this code needs to get the > topology sorted by itself -- how could a multi-path driver inject > itself into the symlink creation in enclosure.c? I merely meant that our current philosophy is to layer multi-path awareness in a separate driver: dm. There's certainly no expander awareness in dm-mp at the moment, but there could be. It should be quite simple: match the expanders to something like a dm-exp and then basically use the slot information in the expander to construct dm devices for each of the physicals (the rule for dm device creation would be dm-exp slot matching). James -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
