reliability,
might have more delays, more opportunity for broken connections
fault-tolerance,
slight increase in most cases, due to more machines being available
for processing
Arent these two claims contradictory? In the sense that, if chaining callout
servers is supposed to decrease reliability as you suggest (by providing more
opportunities for broken connections and greater delay), then, shouldnt it also
be LESS and not MORE fault tolerant. Chaining, implies that the callout servers
are connected in series. Hence, rather than having "more machines for
processing" being the cause for greater fault tolerance, as you suggest,
doesn't it increase the number of locations where faults can occur and thus
bring down the whole operation. So, IMHO, chaining decreases reliability as
well as fault-tolerance.
-Srini