The question in your title is the one most observability stacks never answer, and the reason it goes unanswered is uncomfortable: a monitoring system that is down and an estate that is perfectly healthy produce the same output, which is nothing. Silence is the ambiguous signal, and it is also the default one.
Which makes the HA/DR topology slightly less important than whether anything at all watches the watcher. The cheap version, where a full standby OMS cannot be justified: an external heartbeat that expects a positive signal from OEM on a fixed interval and alerts on its ABSENCE, hosted somewhere sharing no infrastructure with OEM. Anything living inside the same estate fails in the same event, so it is not a check, it is a mirror.
The question I would put to any setup like this: what does a total OEM outage look like on your dashboards, specifically, and how long could it persist before somebody noticed by a route other than a user complaining? If the honest answer is that it looks like a quiet day, then the HA work is load-bearing rather than nice to have, and that reframing is usually what gets it funded.
The question in your title is the one most observability stacks never answer, and the reason it goes unanswered is uncomfortable: a monitoring system that is down and an estate that is perfectly healthy produce the same output, which is nothing. Silence is the ambiguous signal, and it is also the default one.
Which makes the HA/DR topology slightly less important than whether anything at all watches the watcher. The cheap version, where a full standby OMS cannot be justified: an external heartbeat that expects a positive signal from OEM on a fixed interval and alerts on its ABSENCE, hosted somewhere sharing no infrastructure with OEM. Anything living inside the same estate fails in the same event, so it is not a check, it is a mirror.
The question I would put to any setup like this: what does a total OEM outage look like on your dashboards, specifically, and how long could it persist before somebody noticed by a route other than a user complaining? If the honest answer is that it looks like a quiet day, then the HA work is load-bearing rather than nice to have, and that reframing is usually what gets it funded.