nFor
fault-tolerant persistent state
oPersistent state plus log represents current state
oOnly use the log after a failure
nps
= persistent state, l = log, s = state
os = ps; l
oTo apply an
update u: l := l; u
writing a redo program
oTo install an update u: ps := ps; u
oNeed s' = s, so ps; u; l
= ps; l
ou; l = l is sufficient
nThe
bet: No crash. An easy win
nRep:
state = persistent state + log