It's not default because its code path is badly inefficient. I'll accept design criticism, though I think doing it more efficiently would recquire some hardware assistance, like the pp_alua does. Regards, cvaroqui On jeu, 2005-04-28 at 14:42 -0400, goggin, edward wrote: > Just wondering why the pp_balance_units path priority callout is not > the default get_priority callout instead of /bin/false which simply > assigns a priority value of 1 to every path. This seems especially > true for the symmetric (active-active) storage arrays which by their > very definition don't have their own built-in preferential paths for a > logical unit. > > Seems like pp_balance_units assigns a higher priority to paths > connected to SCSI targets which it anticipates will be under-utilized > when considering the path accessibility of all mapped devices > accessible on the same storage system from the same host. > It will also yield the same results as /bin/false will (that is, all paths > will have the same priority) in the case where all mapped devices > on a given storage array are accessible from the same set of targets > on that array. > > Pp_balance_units does appear to have a deficiency in that it does > not take into account the impact on these storage system targets > from other hosts (admitably difficult to do) accessing these same > (cluster case) or different SCSI logical units. > > -- > > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel -- christophe varoqui <christophe.varoqui@xxxxxxx>
