MacBook macOS update not caching from Mac mini?

Preamble: my thoughts punched up with the help of an Ai / LMM model to make it more coherent

I think your observation gets to the heart of why Content Caching is harder to evaluate today than it was ten or fifteen years ago.

In the past, the value was obvious. A software update was downloaded once, cached locally, and then served repeatedly to multiple Macs or iOS devices. The bandwidth savings were easy to see, and the cache hit rates were often extremely high because many devices were requesting nearly identical content.

Today, Apple distributes a much more fragmented set of assets. Firmware is often specific to a particular model, architecture, or device family. An M1 MacBook Pro, an M3 MacBook Pro, and an M4 Mac mini may all be installing the same macOS version, but they are not necessarily downloading exactly the same components. The same is true across iPhones, Apple Watches, and other Apple devices. As a result, Content Caching does not always achieve the dramatic efficiencies it once did.

Your workflow of downloading the full installer once, copying the "Install Tahoe" application to an external drive, and then deploying it to your other Macs is actually a very good example of this reality. You are effectively creating your own distribution mechanism and guaranteeing that a large portion of the download occurs only once. For major macOS upgrades, especially across different Mac models, that approach can be more predictable than relying entirely on Content Caching.

At the same time, I would be cautious about concluding that caching has lost its usefulness. Looking at your screenshot, the cache served approximately 38.8 GB of data over the last 30 days, while total data served to clients was 83 GB. That means nearly half of the requested content was delivered locally rather than fetched again from Apple. Even if the absolute number does not seem enormous by modern broadband standards, a cache hit rate approaching fifty percent is still quite respectable for a household with a mix of different Apple hardware.

That is why I tend to view "Data Served From Cache" as the most meaningful measure of real-world value. It answers a very practical question: how much internet traffic did the cache prevent? In your case, the answer is almost 39 GB over the past month. If you disabled Content Caching tomorrow, that traffic would almost certainly be pulled from Apple's servers instead.

What I find equally interesting is the relationship between "Data Served From Cache" and "Data Served To Clients." The raw number of gigabytes saved tells you the benefit, but the ratio between those two values tells you how effectively the cache is operating. In your example, the cache is satisfying roughly 47 percent of client requests. That gives a better sense of efficiency than the bandwidth figure alone.

The other statistic that stands out is the cache pressure. Your maximum cache pressure is only 20 percent, which suggests the cache is not struggling to retain content. It is not constantly evicting data to make room for new downloads, and it appears to have sufficient storage allocated for the workload it is handling.

So if I were trying to judge the value of Content Caching in your environment, I would not focus solely on the fact that firmware and model-specific downloads have reduced some of its historical advantages. Instead, I would ask a simpler question: "How much traffic would my internet connection have carried if the cache did not exist?" Based on your numbers, the answer is almost 39 GB over the last month. That seems like a fair indication that the service is still doing useful work, even if the benefits are less dramatic than they once were.

In other words, I do not think Content Caching is obsolete. I think it has shifted from being an obvious and substantial bandwidth-saving tool into a quieter background service whose value depends heavily on the mix of devices in the household. Your numbers suggest it is still earning its keep.

No, that is not how it works with the current macOS builds.

You need to use that Mac's Software Updater to find the compatible build for that Mac model.

see > Update macOS on Mac - Apple Support

When we factor in Firmwares specific to each make and model

It would seem reasonable to conclude " Caching " may or may no longer be a viable option

The installer needs a stable internet connection to download macOS and get firmware and other information specific to your Mac model.

Personally, using a M5 Laptop, M4 Desktop and a M2 Desktop

When a new update is made available

Sometimes I will purposely and manually download the Full Version on one machine

Copy and Paste the " Install Tahoe app " onto reliable external drive

Move the drive from one machine to another machine

Copy the Installer to the Applications folder on the other two machine

Ready to install at a time of my choosing

In effect, 1 Download used on 3 machines

A07570 wrote:

If I update a Mac mini running cache services to macOS 26.5, and then a day or two later update a MacBook on the same network, shouldn't I expect that update to be served from cache on the Mini? I would expect it to be reflected in the "Last Hour" statistics, under "Data Served From Cache"? I'd also expect the update file to be quickly loaded on the MacBook?

Never used it myself...

See if there is anything here:

Set up content caching on Mac

Change Content Caching settings on Mac

Change content caching Peers options on Mac

A07570 wrote:

Ok thanks, I've always used Software Updater, but it used to go much faster. So it's not cached anymore because each Mac model now has a different build.

Also, after downloading the updater, unless it is used within a day or so, it seems to age out and no longer works, so then a "new" one has to be downloaded.