According to Apple, Big Sur’s system software updates are one of its features, making it “easier than ever to keep your Mac up to date and secure.” I have yet to hear from a user who agrees: we’re only too well aware of the size of Big Sur updates, and the disruption they cause. Furthermore, Apple no longer supplies standalone updaters for macOS 11.x, so the only way to economise on downloads across multiple Macs is to run a Content Caching server. For these and other reasons, many of us have found Apple’s claimed improvements far from easier or quicker.
Look in the full list of new and improved features of Monterey, and there’s no mention of software updates, implying that there aren’t intended to be any significant changes, and our complaints about Big Sur’s updates have fallen on deaf ears after all. This article reassesses how Big Sur’s “easier” system is working out now, and what comes in the future.
The current version of Big Sur is 11.4, well over half way through its cycle, with the expectation that there are two further minor updates to come before it receives only security updates, and Apple wants us to upgrade to Monterey and start a new update cycle. Over that period, a typical Intel Mac has already downloaded and installed almost 26 GB of macOS updates (excluding security data files which are pushed separately), and the equivalent for an M1 Mac is just over 36 GB – an average of 5 GB per month of macOS updates.
Compared with cumulative total updates in Catalina and Mojave, Big Sur has required far larger updates than any version of macOS before. An M1 Mac running 11.4 has installed three times as much as an Intel Mac would have at this stage with Mojave, and more than twice as much as Catalina.
Comparison between Big Sur and previous major versions of macOS is clear on this graph of cumulative total macOS updates by minor version number. It’s likely that, over the whole of its first year, Big Sur will have required an M1 Mac to have downloaded and installed well over 40 GB of updates in all.
Local content caching
For those with multiple Macs and limited by bandwidth or capping, one mitigation is to run a Content Caching server. However, the benefits of that are more limited with M1 models, which seem always to have to download about 900 MB of each macOS update direct from Apple’s servers. Intel models are more efficient: not only are matching updates 0.5-1 GB smaller than those for M1 Macs, but the whole of each update can be obtained from your local content cache.
Taking my own network as an example, a user with two Intel Macs and two M1 Macs to update each time from macOS 11 to 11.4 could have reduced their total download from 124 GB to just 45 GB. Although that’s an impressive saving, the average download for each Mac is 11 GB, which is almost the same as an individual Mac updating Mojave from 10.14 to 10.14.4. The Content Caching server thus only mitigates the severe inflation in update sizes since Mojave.
Loss of standalone updaters
Big Sur supports only two forms of system software update: incremental updates delivered by Software Update or
softwareupdate, and full macOS installers, which typically weigh in at over 12 GB. Previous versions of macOS have also been supported by two forms of standalone update:
- delta updates, which perform a single increment, from the previous release version;
- Combo updates, which perform the whole update from any previous minor release of that major version of macOS.
Because Big Sur updates rely on different mechanisms to install and perform the update, which don’t transfer to Installer packages, Apple hasn’t offered any standalone updaters for Big Sur. Not one. The nearest equivalent to what would previously have been a package of perhaps less than 1 GB is therefore the full macOS installer of over 12 GB. Apple has shown no interest whatsoever in changing that, and it isn’t currently listed among the features of Monterey.
Big Sur in maintenance
According to unwritten but longstanding understanding, with the release of Monterey this autumn/fall, Big Sur will receive two years of security updates. These usually consist of small batches of patches to more prominent outstanding vulnerabilities, typically coinciding with updates to the current major version of macOS, perhaps six over the course of a year.
If Apple doesn’t change the methods for delivering and installing updates to Big Sur, for an M1 Mac that would amount to an annual download size of a little less than 20 GB, and a total over the three year lifecycle of around 80 GB, which far exceeds any previous version of macOS, and I suspect any other widely used operating system. Although I can’t find reliable estimates of the carbon cost of this type of download, figures of 3 kg per GB are suggested. Thus, the total cost of Big Sur could amount to around a quarter of a tonne of carbon dioxide per M1 Mac. This will vary considerably between individuals, and according to the footprint of the servers used to deliver all those updates.
One thing’s for sure, though: over those three years, Big Sur updates will have been the most irritating and time-wasting of any version of macOS to date. I’m certain that’s not what Apple meant by “easier than ever”.