3 ms·

You still have a single point of failure with the haproxy though. i.e. if the Data Centre with the proxy is taken out (same probability as the prod site), then

You still have a single point of failure with the haproxy though. i.e. if the Data Centre with the proxy is taken out (same probability as the prod site), then the service would stop. Even if you install multiple haproxies you're either back to the DNS scenario, or a more expensive solution as you were suggesting. If you are with a large-scale multihomed hosting company, then you might be able to manage with an IP address takeover between sites (ie. the passive haproxy takes over the IP of the master in an event of heartbeat failure). I've not seen this as an offering for the most part though (at smaller outfits anyway).

brk 18y ago
You still have a single point of failure with the haproxy though. i.e. if the Data Centre with the proxy is taken out (same probability as the prod site), then the service would stop. That's why I said a true multi-homed datacenter. Reduces the chances of a single-point failure taking everything out. It is going to be somewhere in cost and resiliency between relying on DNS and "doing it right". In all reality (and my own experiences) data-center outages to various "natural/random disasters" are far less common than outages due to just basic employee stupidity. While I was building up my org/website, I would spend more time worrying about resiliency against stupidity vs. plane crashes.
- jwilliams 18y ago
  Well I guess my logic is that if you have each site either multi-homed, or at least on different networks (a given anyway), then you can have a LB at each site with the same net result - this is basically your vanilla active-active scenario. In either case - Unless you go for a high-end solution, the catastrophic-scenario-DNS-juggling doesn't really go away. As for the relative risk, I agree. The problem is the risk approaches companies use tend to make this kind of thing compulsory for them. All the raw calcs I've seen rarely justify this kind of expense - the cost-benefit, against, say, a 1 day turnaround to configure a new site (two sites is usually a lot more than double the cost as there is all the other factors e.g. additional/routine testing that's introduced). ... but then companies will factor in less tangible risks, like reputational damage, etc, which can be a bit of black magic... Of course, if you're a bank, or a hospital this might be right, but I suspect in most cases it's off-base.

brk 18y ago

You still have a single point of failure with the haproxy though. i.e. if the Data Centre with the proxy is taken out (same probability as the prod site), then the service would stop. That's why I said a true multi-homed datacenter. Reduces the chances of a single-point failure taking everything out. It is going to be somewhere in cost and resiliency between relying on DNS and "doing it right". In all reality (and my own experiences) data-center outages to various "natural/random disasters" are far less common than outages due to just basic employee stupidity. While I was building up my org/website, I would spend more time worrying about resiliency against stupidity vs. plane crashes.

jwilliams 18y ago
Well I guess my logic is that if you have each site either multi-homed, or at least on different networks (a given anyway), then you can have a LB at each site with the same net result - this is basically your vanilla active-active scenario. In either case - Unless you go for a high-end solution, the catastrophic-scenario-DNS-juggling doesn't really go away. As for the relative risk, I agree. The problem is the risk approaches companies use tend to make this kind of thing compulsory for them. All the raw calcs I've seen rarely justify this kind of expense - the cost-benefit, against, say, a 1 day turnaround to configure a new site (two sites is usually a lot more than double the cost as there is all the other factors e.g. additional/routine testing that's introduced). ... but then companies will factor in less tangible risks, like reputational damage, etc, which can be a bit of black magic... Of course, if you're a bank, or a hospital this might be right, but I suspect in most cases it's off-base.