Hello Yang, > > Actually, you're not alone here; several other storage array setups > > suffer from the same problem. > > > > Eg if you have a site-failover setup with two storage arrays at > > different locations the problem is more-or-less the same; > > both arrays potentially will be displaying identical priority > > information, despite one array being remote. > > > > It's up to the value set of the argument "latency_interval".For > example, > If latency_interval=10ms, the paths will be grouped in priority > groups > with path latency 0-10ms, 10-20ms, 20-30ms, etc. If the argument > "latency_interval" is set to appropriate value and the distance > between > two arrays is not enough far, two priorities may be the same, But > it's > OK, because between two arrays, the gap of average path latency is > very > small and tolerable. I wonder if it would make sense to use "logarithmically" scaled latency intervals here. It wouldn't make a large difference whether the latency is 1ms or 2ms, but if we have paths where the latencies differ by order of magnitude, it would be very important to make a distinction. With the current linear intervals, it would be hard to get this right (us interval size would result in too many intervals, and sec interval size wouldn't allow a distinction between us and ms latencies). By using logarithmic scale, you could setup the latency intevals e.g like this: < 10us, 10us-100us, 100us-1ms, 1ms-10ms, 10ms-100ms, > 100ms IMO that would be better, in particular if the latencies differ strongly between paths. Regards Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
