Just to bring it to your remeberance, ftpcluster is a prototype. Don't expect that everything is working as.

Logging

server, store and replicate write their log information to the file .cluster.log. Inspect this file if you want to know what was done by which program. But this file receives only basic logging and error messages.

Debugging

server supports the debug option -d. This is for debugging FTP conversations between the cluster, the client and the nodes. If debugging is turned on server writes complete protocol information to the file .logs/server-<sid>.log where <sid> is the server's timestamp with it's process id appended.

The server's session id is sent from the server to the client as part of the initial greeting message. If you didn't plan to debug your session and because of that didn't notice your sid you can query it with the 

ftp> SITE SID
command. Furthermore, if you want to turn debugging during a running session on or off you can use 
ftp> SITE DEBUG ON|OFF
store and replicate support the -d option as well. But in case you run on of these programs from the command line you may set -i to get the debug information to stderr.