Efficiency trades off against resiliency
blog.nelhage.com
Efficiency trades off against resiliency
1–10 of 66 posts
Re: Efficiency trades off against resiliency
#2Now apply this same reasoning to, say, hospital capacity.
Some things need to optimize for the ability to absorb peak load, not steady-state operating costs.
Re: Efficiency trades off against resiliency
#3Maximally efficient is minimally robust.
Re: Efficiency trades off against resiliency
#4Now apply this same reasoning to, say, hospital capacity. Some things need to optimize for the ability to absorb peak load, not steady-state operating costs.
How is peak load defined in a hospital? (I assume you mean patients. I apologize if that is incorrect.)
Re: Efficiency trades off against resiliency
#5Now apply this same reasoning to, say, hospital capacity. Some things need to optimize for the ability to absorb peak load, not steady-state operating costs.
How is peak load defined in a hospital? (I assume you mean patients. I apologize if that is incorrect.)
There will be different definitions for related concepts but I reckon the parent comment is referring to "surge capacity"
Re: Efficiency trades off against resiliency
#6Yes I code, a few million+ SLOC in geophysics | imaging | GIS | et al, but more and more I consult on policy with companies and local to Federal government in Australia on the back of having an engineering | applied math background.
Agricultural and farmers might seem inefficient but they add national resiliency.
Pre COVID meat packing in the USofA may have been hyper efficient on paper but it broke hard under stress; too many concentrated assembley lines that put too many people too close together in too few places in total.
Day to day one of my favorite redundancies is the triple bowline for multiple anchors - under load if one anchor fails the knot rebalances load to other anchors and slowly contracts the "dead" loop with no sudden jerk.
Re: Efficiency trades off against resiliency
#7While I generally agree that the pattern this article describes is real (there's some degree of tradeoff between robustness and efficiency), I've frequently seen engineers fall back on that logic rather than actually thinking about the specific problem they're facing, and spending five minutes trying to come up with a creative solution.
For example, talking about the CPU utilization of a web service, your service can perform a mix of time-critical work (serving queries) and background tasks (indexing, etc). If a server is running at 100% CPU but 30% of that is spent performing background work, the amount of slack available for a sudden surge in demand is 30%, and I suspect it's almost never the case that a large service sees an unexpected 30% load increase in less time than it takes to boot another machine, so such a system could be both efficient and robust with few downsides.
Implementing that system isn't as easy as just throwing more Kubernetes nodes at your problem, especially given that the ecosystem of tooling isn't designed to make it easy. For example, it would be really nice if load balancers used realtime performance metrics to balance traffic at a millisecond level.
Perhaps the real lesson is that "many of the easiest ways to achieve robustness involve sacrificing large amounts of performance", but I reject the idea that we should use that as an excuse to accept terrible performance, with all the monetary and environmental impacts it brings.
Re: Efficiency trades off against resiliency
#8Now apply this same reasoning to, say, hospital capacity. Some things need to optimize for the ability to absorb peak load, not steady-state operating costs.
How is peak load defined in a hospital? (I assume you mean patients. I apologize if that is incorrect.)
For a public health system you run the stats, using the $ cost of a life (or equivalent for a well life vs. sick life). Sounds sinister but ultimately they have so many $ and need to decide how to optimise that money.
Re: Efficiency trades off against resiliency
#9Maximally efficient is minimally robust.
This also applies to supply chains and economies in the whole.
Re: Efficiency trades off against resiliency
#10Now apply this same reasoning to, say, hospital capacity. Some things need to optimize for the ability to absorb peak load, not steady-state operating costs.
How is peak load defined in a hospital? (I assume you mean patients. I apologize if that is incorrect.)
> How is peak load defined in a hospital?
Same as everywhere else - largest demand on resources. For a hospital, the resources are staffing and equipment (rather than cpu/storage/ram). An MRI machine is cheapest when you have as many scans as possible for a given level of staffing - reducing the time per scan from 6mins to 5mins means that you can get 20 extra patients scanned per 8 hour shift (with one machine).
In support of the initial commenter's point ("Some things need to optimize for the ability to absorb peak load, not steady-state operating costs"), for hospitals, you need look no further than covid - horrendous health outcomes for routine things, because the capacity was soaked up dealing with respiratory virus. And if you disagree with that (you're wrong), look no further than a strong flu season - staffing capacity that is totally fine for a random august is nowhere near adequate. Or look at Saturday night in any Emerg - there's a huge peak in emergency medical situations from drunk people doing stupid things.