Managed to do another round of measurement with hardware and software cache disabled.  Before LUN migration started: 672.27 IOPS, Average latency 1.474ms 99th %-tile = 9.232ms 3-nines = 37.597ms 4-nines = 140.384ms max = 140.384ms  During LUN migration on speed ASAP: 626.80 IOPS , Average latency 1.585ms  99th %-tile = 12.004ms 3-nines = 41.780ms 4-nines = 97.886ms 5-nines = 174.939ms 6-nines = 1036.318ms max = 6772.611ms  So performance does take a slight hit.  Thanks!
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 [IMAGE], Average latency 0.013ms [IMAGE] %-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
VNX LUN Migration - performance impact on source LUN