Biggest Sur by far

With this week’s macOS security updates, we move into the next cycle, Big Sur joining Catalina with security updates only for the next year, and Mojave left to fend for itself in the security jungle. I can now produce comparable final accounts for the support costs of each of those three in terms of downloaded macOS updates.

As you’d expect, macOS Mojave was by far the smallest, with a total of only 21.5 GB for its cycle. Catalina was half as big again, but nearly 7 GB of its total of 32.2 GB followed the 10.15.6 update.

Apple was clearly not joking when it chose to name macOS 11 Big Sur, as it’s the biggest by far: nearly 37 GB for Intel Macs, and an astounding 50 GB for M1 models, which averaged almost 1 GB per week of downloaded updates.


The value of using the macOS Content Caching Server is also clear. With two Intel Macs and two M1 models, over the year I would have downloaded a total of 174 GB had I not been running that server, which reduced to about 63 GB with the server running. That’s just over a third of the total without the server.

Another way of looking at the Big Sur figures is in terms of payload efficiency. The minimum update size for Big Sur on Intel Macs is 2.2 GB, and on M1 Macs 3.1 GB. Taking those as pure overhead, Intel Macs received 10.3 GB of update content over the year, and M1 Macs 12.9 GB. Those mean that only 28% of the downloaded updates for Intel Macs were the active payload, and for M1 Macs that fell to 26%. With more than 70% of each download being overhead, payload efficiency is extremely poor.

Over the coming year, the prospects are no better. Intel Macs left with Big Sur security updates are likely to require at least six of those at a minimum of 2.1 GB each, making nearly 13 GB in overhead alone. Unless Apple drastically improves macOS updates, M1 Macs upgraded to Monterey are probably facing another 50 GB of updates in the same period.

The time has come for Apple to devote a little more attention to its users’ needs. Why should we have to download and install 3.1 GB of macOS update just to get a minimal security update of a few megabytes? Can no one see how ridiculously inefficient this has become?