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As an engineer, I get pissed whenever I see 100% uptime, or eleven-nines, nine-nines, or other impossible targets. Like, how am I supposed to design a system wi
by klodolph 7y ago
As an engineer, I get pissed whenever I see 100% uptime, or eleven-nines, nine-nines, or other impossible targets. Like, how am I supposed to design a system with numbers like that?
- Lorin 7y agoDeploy once, never update, and deploy a missile defense to prevent backhoes from digging up fiber?
- klodolph 7y agoAh yes, missile defenses, like the MIM-104 Patriot: https://en.wikipedia.org/wiki/MIM-104_Patriot#Failure_at_Dhahran https://en.wikipedia.org/wiki/MIM-104_Patriot#Failure_at_Dha...
- JaimeThompson 7y agoYou honestly think a missile defense system will work. Backhoes are much more creative than that. You will need defense in depth, roaming patrols, as well as air and satellite based monitoring assets.
- jacques_chester 7y agoAnd then the fibre will get cut by a building crew working on a guard tower.
- ohyeshedid 7y agohttps://i.imgur.com/rDW7W3d.png https://i.imgur.com/rDW7W3d.png
- haggy 7y agoYou don't. Like others have said SLA's are a sales tool, not an objective for the engineering team to achieve.
- bifrost 7y agoI agree, advertised SLAs are garbage. Agreements to uphold past performance are much better.
- cortesoft 7y agoSLAs aren't for engineers, they are for financial people to make agreements on payments for downtime.
- klodolph 7y agoGood SLAs are also for engineers.
- dserodio 7y agoThat's what SLOs are for
- klodolph 7y agoIf you only look at the SLOs you are a junior engineer working for someone else making the big decisions. If you are designing a system you want to look at the SLA. Engineers are not just assembly line workers that consume specs and spit out parts. Nothing wrong with just using SLOs, but if you are a technical lead or senior engineer, you should have the big picture.
- toast0 7y agoThe thing is, a real SLA will have things like time to detect errors and time to mitigate, time to repair, etc. 100% uptime doesn't necessarily mean nothing failed, it means the failure detection and mitigation worked within the allowed windows. In a typical internet environment, that means allowing connections to die when the server they're connected to dies. It's would be possible to handoff tcp connections, but nobody does it. If you want to get close to those numbers, you need to have a real reason, and then you need to make sure you have a good plan for everything that can go wrong. Power, routers, fiber, load balancers, switches, hosts, etc. And then do your best not to push bad software / bad configuration. Bare metal on quality hardware with redundant networking goes a long way towards reliability, once the kinks are worked out.
- jaclaz 7y agoExcuse my curiosity, but what are numbers that you would find acceptable as targets? Or - if you prefer - what is the "reasonable" percentage of issues - timewise - for an internet service?