Tech Froth: SSD Upgrade and Dual-booting Sierra and Mojave

My MacBook Air is seven years old. I’ve looked after it pretty well and to the casual eye would still look brand new (the magsafe cable is the only thing that has worn a little). Though I increasingly use my iPad for day-to-day stuff, I rely on the Air all the time. I resisted upgrading OSX for about three years. Deliberately so.

There are a number of apps I use that I know will stop working if OSX upgrades. Some of the apps have moved to subscriptions that are prohibitively expensive and I can’t afford to use them. On the other hand, there are newer apps I use on iOS that won’t install on Sierra, the version of OSX I’ve stubbornly kept using.

I’m aware, too, that the next version of iOS (13) and OSX (Catalina) are going to introduce features that continue to integrate the two operating systems. It’s already pretty good and I rely on being able to work on something on my iPad or iPhone and then immediately be able to open it on my Air when I get home. iCloud integration has become so good that I seldom use Dropbox or Evernote for storage.

I’ve known for ages that if I’m going to continue using the Apple ecosystem then I have to upgrade my Air… but don’t want to lose those apps. So what have I done?

Well, after a lot of research, I found that it’s possible to cheaply upgrade the internal SSD hard drive of the Air and dual boot it so that I can use Mojave, the current version of OSX and swap to Sierra when I need to use the old apps (which isn’t all the time).

What I used:

  • a full installation copy of OSX Mojave
  • Superduper!, a drive cloning app
  • an M.2 NGFF SATA to A1466 adapter
  • an M2 to USB adapter
  • a Western Digital 500gb M.2 SSD
  • T5 and P5 screwdrivers

The SSD replacement was surprisingly quick: 20 minutes to install the OSes, 10 minutes to physically remove the old SSD and install the new one. The longest time – around an hour-and-a-half – was spent tweaking Mojave and installing the apps I use freshly. iCloud did most of the work.

I was genuinely surprised how easy it was. Naturally, I was concerned about damaging the Air or losing my current installation of Sierra. Nothing at all caused an issue.

First I slotted the new SSD onto the USB adapter and partitioned it so that I had three drives (so I can dual boot and, later maybe tri-boot with another OS): Mojave (260gb), Sierra (130gb) and “Spare” (110gb). I then used Superduper! to clone the existing Sierra drive to its partition on the new SSD.

The M.2 SATA adapter was then connected to the new SSD (it needs this to plug into the Air):

I used the P5 screwdriver (Apple use special screws) to take off the bottom of the Air. I made sure I disconnected the battery. Inside it was very dusty, so I gave everything a quick clean:

Once reassembled, the Air booted into the “old” Sierra and from there I could install Mojave into its partition:

Again, I’ll use the word surprisingly to describe how quickly Mojave installed and was up and running:

Of the entire operation the thing that took the most time was typing in account details into Filezilla and Unison (I couldn’t get them to export the info). Everything else went smoothly.

It’s the first time I’ve done any tech stuff like this in years. I used to build and tinker with desktop PCs years ago and used to get frustrated with the problems I had. (Though I did grimly enjoy the problem-solving I had to do.) I’d expected problems but (so far) things have just worked.

My only regret is that I settled for a 500gb SSD rather than a 1tb just in case. With a bigger drive I could have enabled a quad or penta-booting macbook…