about the computation of the Total Latency I have already written an answer into some other thread here, so you can review following:Re: meaning of "other " latency
In general, if there is a LUN that reports Read latency very big and Write latency small, the Total latency cannot be the max value, and also it cannot be summary of those two. It should be some value that informs end user about how the LUN responds based on the R and W latency but also I/O must be taken in account here. The Total latency here means "kind of" weighted average of metrics (Read, Write) where it takes the particular latency metrics the device reports and as a weight is used the Total I/O operations. Not saying it is exactly weighted average, the formula is more complicated, but it can be very close to it and can be used for illustration.