4 Replies Latest reply on Mar 29, 2016 1:59 AM by Lubomir Krausko

    meaning of "other " latency

    acmon

      Hi,

       

      I just installed SRM on my Orion server. I added a NetApp running clustered mode and start to notice some of volumes have very high latency (instead of a few msecs, they are ~200msecs). Only some of the volumes on the NetApp have such high values and the NetApp is on the same network as the SRM server. Drilling down to the latency graph of one of the volumes, it shows:

       

      Total: 182 ms

      Read: < 1ms

      Write: < 1ms

      Other: 195 ms

       

      First of all, what is "Other"?

       

      Second, the numbers do not add up. Shouldn't "total" > the other numbers?

       

      Any suggestions are very much appreciated.

       

      Thanks,

        • Re: meaning of "other " latency
          silverbacksays

          I expect this will be locks/waits where I/O is contended. With the other query, I'd expect them to add up too, but maybe it's an average over the timescale show in the resource?

          • Re: meaning of "other " latency
            Lubomir Krausko

            Hi,

            so in general SRM does not do any measurement nor load on the device itself. SRM only reads counter/statistic values that are on the device itself. It means that it does not matter whether the device and SRM are installed in a one network, the latency SRM displays is only number the device reports with no relation to network.

             

            By these words you can also see, that SRM does not increase any load not traffic on the device itself, SRM only reads statistics from it.

             

            Now the values you are seeing...

            The Other latency is metric, that reports device directly to SRM. It only takes it and displays together with other metrics. So why it is so high is better to find the answer in device itself.

            Is not the Total latency SUM of Read, Write and Other latency? Actually not. In general if there is a volume that reports Read latency very small and Write latency quite big, 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 volume 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 all three metrics (Read, Write and Total) 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.

             

            I do not want to share here a lot of details of that, since this data reporting and metrics availability for each vendor can differ a lot, but I hope I did not confused you too much and brought you some level of information you'd like to know about this.

             

            Thanks you for this question and interest!

             

            Regards

            Lubo