[Jensson]

> There is definitionally no more efficient way to improve the performance of a system than sequentially targeting each new bottleneck in its performance and nothing else.

You are making an extremely strong statement here, how do you define "bottleneck" for this to be true? Many slow systems doesn't have bottlenecks, they are just slow overall with no bottlenecks.

[llamaimperative]

And this is the key insight that "everyone knows" and you apparently do not: every system has exactly one bottleneck at any given point in time. The bottleneck can move, alternate, or not be so significant relative to other near-bottlenecks that it's hard to spot, but there is exactly one.

Your perception that "there are no bottlenecks" is exactly the perception Deming set out to disprove.

Riddle me this: how can a system perform faster than its single slowest component?

It cannot. Ergo, there is a single bottleneck that sets the pace of the entire system.

[RaftPeople]

> every system has exactly one bottleneck at any given point in time.

Consider this system that has 5 sequential steps with these durations:

Step 1: 10 seconds

Step 2: 5 hours

Step 3: 7 seconds

Step 4: 5 hours

Step 5: 18 seconds

It would seem that both step 2 and step 4 are both bottlenecks. Are you saying that in reality one of those 2 steps would not typically be the exact duration so one of them would be considered the actual bottleneck?

[ulyssys]

In this example, assuming sequential steps, if step 2 must be performed before step 4, then it is step 2 which is the bottleneck.

After step 2 has been optimized, step 4 becomes the new bottleneck—assuming that optimization of step 2 is satisfactory.

While both steps 2 and 4 contribute to a slow system, a bottleneck means something else entirely: it is the single most significant point of slow down for the rest of the process.

To put it another way, it’s hindering the overall execution. If both use the same amount of time, then whichever is closer to the front of the process is by definition hindering more of the process.

[Jensson]

> every system has exactly one bottleneck at any given point in time

What, no they don't. Does a straight glass have a bottleneck? No, most bottles have it, but not straight glasses, hence not every system has a bottleneck.

The same applies to IT systems, there the topology is much more complex so often can have many bottlenecks, or sometimes fewer etc.

> Riddle me this: how can a system perform faster than its single slowest component?

A perfectly optimized component can't be a bottleneck but can still be the slowest component, trying to optimize that further will not speed up the system at all.

Here we see that you will miss a lot of optimization opportunities since you think the slowest component is the bottleneck, and not looking further.

[llamaimperative]

I don't find the glass <> IT system analogy compelling (or even sensical) at all.

Describe to me how an IT system can produce results (e.g. tickets closed, if you wish) at a rate higher than the processing rate of the slowest component.

> A perfectly optimized component can't be a bottleneck but can still be the slowest component, trying to optimize that further will not speed up the system at all.

Correct -- but neither will optimizing anything else! That's the whole point!

[Jensson]

> Describe to me how an IT system can produce results (e.g. tickets closed, if you wish) at a rate higher than the processing rate of the slowest component.

It can't, but the slowest component can be perfectly optimized and thus not be a bottleneck. You would fail to find a real bottleneck in this case, since you are just looking for the slowest one, hence I have proven that your statement above was false, there are cases where the optimal strategy is not to just look at the slowest component.

If you have some other definition for bottleneck we can continue, but this "the slowest component" is not a good definition.

[llamaimperative]

No, what you've done is you've failed to find a way to improve the system's behavior further. If you have the slowest component and you can't make it faster, then congrats: you cannot make the system faster.

You cannot build cars faster than you can mine metal, nor faster than you can put stickers on the windows on their way out the factory. You are done optimizing.

[Jensson]

> If you have the slowest component and you can't make it faster, then congrats: you cannot make the system faster.

That isn't true, I can take the next slowest component and make that faster and now the system is faster.