I made a small test with 3 infinispan nodes participating in the same cluster, each putting a key-value into the cluster. The concurrency level is set to 3. cluster mode is DIST_SYNC. All the entries show up on all the nodes as is expected.
The concurrency level does not have to do with data redundancy, but rather with the expected amount of threads that would concurrently access the code. It's the numOwners attribute on hash element that defines the number of nodes on which data will be held:
<hash numOwners="3" rehashWait="120000" rehashRpcTimeout="600000"/>