Hi Martin, Thanks a lot. It's a good idea. The updated patch will be sent later. Regards, -Yang On 2017/6/9 16:05, Martin Wilck wrote: > 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 > > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
