Hi Prasanna,
The format to use the APItest tool is :
apitest -x <IP.XXX.XXX.XX> <USERNAME> <PWD> <API>
you can also use the -X (uppercase instead of lowercase) option instead of -x to get the complete raw XML.
So in your case the command would be :
apitest -x <IP address> <username> <pwd> disk-list-info
-Aashray-