XCOPY might not be in use during volume population for various reasons: 

1. there is no support by the storage, like Dell PowerFlex
2. storage array configuration prevents t10 altogether, and needs to be switched on - like Hitachi Vantara
3. vmkfstools decides to fallback due to errors during xcopy, like multipath errors (some search results show this can happen - citation required)
4. pure network copy - using a source and target from separate arrays must fall back to host reads and writes, hence no xcopy, like copying from VMFS store on HP, to a volume on Dell PowerFlex. 

Some cases here are not expected, and we would want to get an indication if something went wrong and at the minimum log a WARN message. 

Right now  there is no tool to indicate that, oustide of esxtop with 'u' 'f' 'o' , to get the CLONE_RD and CLONE_WR fields for the source and destination.

Goals:

• investigate how can we make the XCOPY indication programable
• if found an effective way, return that indication as part of the task status in the vmkfstools-wrapper