In order to make web2py work with a load balancing and multiple installation, they all need to share the same folder. For example via NFS.
Notice that you also eed NFS file locking to work, hence you need the
Quote: "Nlockmgr is an NFS server daemon that enables file locking and sharing. However, it is not supported by all hosts. If this daemon is not available on your host, enable it or disable file locking and file sharing in the Reflection NFS client. If you want your users to be able to share files, you need the nlockmgr daemon to prevent file corruption."