How to check the cache_peer sibling is working?

["John Lui" <johnluicn@xxxxxxxxx>]

I used two squid server (A,B) as sibling,the
icp_port,query_icmp,icp_access,cache_peer has been setted.

query_icmp on
icp_port 3130
cache_peer A(/B) sibling 80 3130 proxy-only
icp_access allow All


One object has been cached by  server A and not cached by server B.
when i want to get the object from server B,the X-Cache from server B
showed that the object was read from the original server not the
server A.
What is wrong with my operation?
Thks                   John