> Is there a way to find  quickly which storagepool each client belongs to .?

The 'query occupancy' command will provide information on which storage
pools a client is currently using. If you use migration to shift backup
files from an initial destination pool to a long term pool, the query
command won't necessarily report the initial destination pool. The query
command won't warn of cases where a client could start using a new pool
any time because of changes in the include/exclude statements or because
of new files that match an include that did not apply to any previously
existing files.