When should you upgrade to High Sierra? (Updated)

Note: I wrote this article just before Apple released a very important note to prepare system administrators for the release of High Sierra. I have now revised it completely in the light of the information provided by Apple.

High Sierra – macOS 10.13 – should be released later this month. Should you be among the early adopters, eagerly waiting for it to appear in the App Store, installing it on the day of release? Or should you resist temptation, sit back, and wait for 10.13.1 or later?

Unless you have been brave (or foolish?) enough to be a beta-tester, you’re likely to have to wait a couple of weeks or more anyway. Apple hasn’t announced when High Sierra will ship, and on past form is not going to. Its ‘event’ on 12 September is centred on new iPhones, and will most probably be accompanied by the release of iOS 11.

Last year, Apple released iOS 10 on 13 September, following it with Sierra a week later. The previous year, El Capitan was released two weeks after iOS 9. So High Sierra is most probably going to be released between 19 and 26 September. [See note below: Apple has confirmed the date as 25 September.]

Who benefits most from APFS?

The most substantial change in High Sierra – and possibly the only really good reason for wanting to upgrade – is the introduction of Apple’s new file system APFS. This should be your major deciding factor as to when you upgrade. If APFS offers you little other than the risk of problems with older apps and more, then you should wait a while to let the dust settle, and prepare yourself more thoroughly. If APFS promises to be a significant advantage, then you should think seriously about being an early adopter.

If APFS is not yet offered for the startup volume of your Mac, then there seems little point in upgrading to High Sierra until you can convert to APFS – unless you can think of another good reason. According to Apple’s latest note, the first release of High Sierra will only convert startup volumes which are on SSD storage, not on Fusion Drives or old-fashioned hard disks.

If your Mac has a Fusion Drive, it should eventually benefit from using APFS: currently these drives work using an intermediate technology, CoreStorage, which pretends that they are a single drive. When it is ready for use on Fusion Drives, APFS should do without CoreStorage, bringing performance improvements.

For Time Machine users, APFS is a bit more of a mixed blessing. Those with MacBook/MacBook Pro/MacBook Air models who often work away from their backup drives should find High Sierra’s new mobile Time Machine an important benefit, as it makes snapshots quick, painless, and very compact. But regular Time Machine backups will continue to rely on HFS+ drives, and work much the same, for the time being.

Trapped in APFS

There is another catch with this initial release of APFS: Apple warns that any SSD (or flash drive) which is converted to, or formatted in, APFS can only be read by another Mac running High Sierra.

Until the release of High Sierra, that hasn’t been the case. Apple has included support for previous releases of APFS in Sierra, but here makes it clear that the release version of APFS will be incompatible with those, and that it doesn’t intended updating Sierra to support the new version of APFS.

For most users with more than one Mac, this makes High Sierra an all-or-nothing deal. If you upgrade your 2017 MacBook Pro to High Sierra, any external drives which you format in APFS using that will be unreadable by your 2017 iMac with a Fusion Drive which is still running Sierra. Worse still, you will be unable to use your MacBook Pro in Target mode with your iMac.

Sysadmins responsible for many Macs will want to think very carefully before they start upgrading any systems to High Sierra, because of this serious shortcoming.

Hardware acceleration

High Sierra brings support for High Efficiency Video Encoding (HEVC or H.265) to all Macs, but only certain models will enjoy hardware acceleration for it. Apple lists the following:

  • all models introduced in 2017 apart from MacBook Air,
  • MacBook and MacBook Pro models introduced in 2016,
  • iMac 5K 27″ late 2015.

However, of those only the 2017 models have this acceleration for HEVC videos with 10-bit colour.

Other new features such as Metal 2 graphics acceleration, VR content, machine learning, and support for external GPUs are likely to need some time before they become significant in deciding when to upgrade, although Metal 2 should make animated parts of the interface feel brisker from the start.


Beyond APFS and enhanced video and graphics support, most of the changes in High Sierra are intended to be fixes and improvements rather than anything radically new. Photos supports additional editing of Live Photos, Safari improves privacy protection and can block video autoplay, Mail searches work better and its mailbox storage requires less space. None of these are likely to change your mind as to when to upgrade, but could be factors in making your decision.

Those whose Macs are left running all the time will have a keen interest in one aspect: whether it fixes the bug in macOS scheduling and dispatching systems which currently causes automatic backups and other services to fail. I have been trying to discover whether this has been fixed in High Sierra beta releases, but cannot find anyone who has tested for it. Because of the time required for the bug to manifest itself, it is likely to be well into October before we know whether High Sierra solves this serious problem.

There will also be some enhancements in iCloud, with the introduction of file sharing for any documents on your iCloud Drive, and family plans for iCloud storage.


Anyone reliant on ‘pro’ apps will want to hold fire on upgrading until they are confident that those apps don’t break. Apple has already warned that older versions of its Pro apps suffer various problems with High Sierra, and Adobe CC users will want to watch for compatibility information before considering upgrading.

If you use virtualisation software, Parallels Desktop 13 is already claimed to support High Sierra, but VMware Fusion 10 is not due to ship until October, when it too should work well.

Apple claims that High Sierra will be compatible with all Macs capable of running Sierra, although I suspect that some older models may prove a bit more troublesome.


Those most likely to benefit from upgrading early to High Sierra are those with 2017 MacBook Pro or MacBook models, who do not rely on Adobe CC products, but who will use HEVC video compression.

If your Mac doesn’t start up from an SSD, or if you don’t want to upgrade all your Macs yet, then you will probably want to wait until Apple has sorted out APFS properly, and made it compatible with the storage in most of your Macs. Apple has given no indication as to how long that will be.

Note: at its iPhone launch on 12 September, Apple apparently stated that High Sierra will ship on 25 September 2017.

(Revised extensively 1940 7 September 2017, and release date added 12 September.)