Difference between EMCQueueLength and derived caluculation for Queue depth

[Sri]

Hi All,

      Could any one clarify my doubt ?. Common blockstoragestatisticaldata cim class  don't have any queue depth related measures ,But SNIA document suggested to calculate queue depth .It can be calculate from  iorate * ioresponsetime ,at the same time  EMC SMI-s have own property EMCQueueLength in blockstoragestatisticaldata cim class  ,I checked with both values ,but does not match any case 

please suggest me EMCQueueLength   and derived queue length same or not ? otherwise how can we calculate queue depth from existing block storage statistical data cim class ,

if both values different mean please give explanation if time permits

 

 

[Praveen Kumar]

EMCQuelength that you get is a cumulative value. You need to find the delta between two collection

For eg: 

EMCQueueLength at 9:00 = 200000

EMCQueueLength at 9:15 = 300000

TimeElapsed between collection is 900 secs

Actual EMCQueueLength = (30000 - 20000) / 900 = 111.11

Regards

Praveen

[Senthil Kumar]

Hi Praveen / Sri,

• May I know why EMCQuelength is not matching with the derived queue length [iorate * ioresponsetime]?
  
• Which metrics / formula we have to use to get QueueLength values.
  

Thanks,

Senthil

[Jeffery K.]

I also have found that the EMCQueueLength is very high, even when doing delta on it. and doesn't seem accurate. Perhaps the meaning of the value is not the "Average queue length" but rather the number of items put in the queue, over the interval?

Here are the values i'm seeing on a EMC VNX system.Many are 290, which is interesting, since it's close to the 300 second interval (5 minute default). The rest are larger, and some very large. Thoughts?

Metric Name                                                                      Average Min         Max         Std Deviation

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_23 291.18 289.00 299.00 2.59

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_2 291.09 289.00 298.00 2.31

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_14 291.18 289.00 299.00 2.55

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_2 4993.00 4423.00 5822.00 417.00

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_10 291.09 289.00 298.00 2.31

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_6 13113.45 2657.00 55663.00 14536.01

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_6 291.18 289.00 299.00 2.55

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_17 13444.73 1808.00 58519.00 15795.24

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_13 13311.55 1974.00 58786.00 15634.75

Disk Queue Length CLAR+APMXXXXXXXX+Disk+1_0_6 291.18 290.00 299.00 2.55

Disk Queue Length CLAR+APMXXXXXXXX+Disk+1_0_2 291.09 289.00 298.00 2.31

Disk Queue Length CLAR+APMXXXXXXXX+Disk+1_0_3 291.09 289.00 299.00 2.61

Disk Queue Length CLAR+APMXXXXXXXX+Disk+1_0_7 291.18 289.00 299.00 2.59

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_12 14153.27 2884.00 61031.00 15998.29

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_16 13603.55 1639.00 59988.00 16245.95

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_22 291.09 289.00 299.00 2.61

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_7 291.18 289.00 299.00 2.55

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_1_11 291.18 289.00 299.00 2.55

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_7 13864.00 2892.00 58475.00 15172.23

Disk Queue Length CLAR+APMXXXXXXXX+Disk+0_0_3 4436.82 3244.00 13035.00 2732.41