Comparison
Active-activevsActive-passive
Active-active
both sites take live traffic all the time, so you already know the second one works when the first one dies.
Running two or more locations that all serve production traffic simultaneously. Its enormous advantage is that failover is a traffic-weighting change to a system you are already exercising, rather than an untested procedure. Its cost is that write conflicts and data consistency across sites become a permanent design problem rather than a disaster-only one.
Full entry →Active-passive
the second site sits there costing money and serving nothing, and the day you need it you find out which four things were never replicated.
Keeping a secondary location ready but idle, promoted only on failure. It is simpler than active-active because there is one writer, and its weakness is exactly that it is never exercised, so its readiness is a belief rather than an observation. Regular, scheduled failovers are the only thing that turns it from a slide into a capability.
Full entry →