Pfister[1] long ago pointed out that the tendency by the marketing departments to redefine HA terms at will makes Humpty Dumpty[*] look like a paragon of linguistic virtue. To save confusion, we will define:
Fault Tolerance to mean that any user of the service exported from the cluster does not observe any fault (other than possibly a longer delay than is normal) during a switch or fail over, and
Fault Resilience to mean that a fault may be observed, but only in uncommitted data (i.e. the database may respond with an error to the attempt to commit a transaction, etc.).
These distinctions are important, because it is possible to regard a fault tolerant service as suffering no down time even if the machine it is running on crashes, whereas the potential data fault in a fault resilient service counts toward down time.