VNX LUN Migration - performance impact on source LUN

Hi,

I did a LUN migration test from Unisphere Client UI. I wanted to know what is the performance impact, if any, on the source LUN during migration, but the test result seems to say otherwise. I have the performance test output shown below for your interpretation too.

Scenario:

Source LUN is a 500GB thick LUN in a new Pool1 backed by 3 x R5_4+1 SAS 10K drives.

Target LUN is a 500GB thick LUN in a new Pool2 backed by 3 x R10_4+4 SAS 10K drives.

Both pools have no other LUNs, save for the above.

No FAST Cache. No SSD.

Source LUN is presented to VMware ESXi as VMFS datastore. There is an online Windows VM inside.

Diskspd.exe tool is run in the VM for 10 seconds, to set a baseline measurement.

Diskspd.exe tool is run in the VM for 1 hour (same parameters), concurrent to the start of migration, which took 3 hours.

10-sec Diskspd output:

585.39 IOPS, Average latency 1.692ms

%-ile Read (ms) Write (ms) Total (ms)

min 0.020 0.019 0.019

25th 1.006 0.030 0.038

50th 3.059 0.038 0.101

75th 4.766 0.051 3.046

90th 6.086 0.070 5.076

95th 7.615 0.085 6.059

99th 12.441 0.197 9.712

3-nines 32.488 1.962 24.127

4-nines 35.307 2.030 35.307

** truncated... 35.307ms from here onwards

1-hour Diskspd output:

63405.89 IOPS , Average latency 0.013ms

%-ile Read (ms) Write (ms) Total (ms)

min 0.000 0.000 0.000

25th 0.009 0.010 0.009

50th 0.009 0.011 0.010

75th 0.011 0.013 0.012

90th 0.017 0.019 0.018

95th 0.022 0.024 0.023

99th 0.032 0.035 0.034

3-nines 0.096 0.067 0.074

4-nines 5.118 0.903 3.963

5-nines 10.437 1.838 8.029

6-nines 32.265 8.086 25.950

7-nines 100.593 20.107 79.159

8-nines 173.966 88.929 146.311

9-nines 200.945 140.639 200.945

What is the explanation for the high IOPS and low latency, during LUN migration?

Thanks.

- KC