Yes, in order to create compression enabled VSM you will need a connection entry like this below.
conn=multi(192.168.1.94,192.168.1.77)
conn:n2 olive-oyl:dst_n2 compression=enable, - - - -
And SnapProtect( or Protection Manager) will not delete the compression entry only if the following options is not set any value for both your source and destination controller.
dfm host set <hostname-or-id-ip> hostPreferredAddr1=<should be empty>
Check out this BugsOnline for more information.
http://support.netapp.com/NOW/cgi-bin/bol?Type=Detail&Display=381872
Regards
adai