There is a brief detection delay as it detects that the link has failed before it starts the failover. In general, on a decently loaded filer it will take at worst ~30-60 seconds to complete the failover, in general its between 10-30 seconds. On heavier loaded filers the delay may be greater. The 15 or so lost pings you see is fairly normal.
If you're using CIFS, then yes the file transfer will likely fail. However, if you are using FCP, iSCSI or NFS and you have ran the host configuration scripts your I/O should only be delayed temporarily and resume once connectivity is restored. If you haven't ran the host configuration scripts then you may encounter some problems depending on what the default timeout values are.