External SSD or an internal upgrade: what is possible now
· 5 min read
On every current Mac, storage is part of the logic board and cannot be upgraded. Whatever you bought is permanent, which makes external storage the only expansion route.
The good news is that external storage over Thunderbolt is fast enough to work from directly, which was not true a few years ago.
What is actually possible
Current Apple silicon Macs: no internal upgrade. Not by a shop, not by anyone.
Older Intel Macs: some models had replaceable drives. A 2012 to 2015 machine may be upgradeable, and a repair shop can tell you from the model identifier.
Mac Pro and some desktop models: expansion exists in specific configurations.
For most people reading this, the answer is external.
How fast external actually is
Over Thunderbolt, a good NVMe SSD in a proper enclosure runs fast enough that you will not notice the difference for most work: editing photos, working with documents, running applications.
Over ordinary USB, noticeably slower, and still far quicker than a spinning drive.
A spinning external hard drive is fine for archives and backups and frustrating to work from directly.
So the tiering that makes sense: internal drive for the system, applications and current work; Thunderbolt SSD for large libraries and active projects; spinning drive for backups and archives.
Setting it up so it is not a nuisance
Three decisions that make external storage pleasant rather than irritating.
Format it APFS if it will only ever be used with Macs. Use exFAT only if it must work with Windows too. Disk Utility does this, and it erases the drive.
Name it something short. It appears in paths, in Finder, and in scripts.
Decide what lives on it and stick to it. The failure mode with external storage is not knowing which drive has what. One clear rule (photos live here, projects live here) beats a vague intention.
Moving a Photos library
The most common reason people need more space, and it works well.
Quit Photos. Drag the library file from Pictures to the external drive. Hold Option and open Photos, choose the library in its new location, then set it as the System Photo Library in Photos settings.
The caveat worth knowing: if the drive is not connected, Photos cannot open. That is fine for a desktop and a real inconvenience on a laptop you carry.
Moving other large things
Music and video libraries move the same way, with the application pointed at the new location.
Virtual machines run acceptably from a fast external drive.
Time Machine should be on its own drive, not sharing with working files. Choosing a drive for Time Machine covers sizing.
Anything you edit daily is better on the internal drive if it fits.
The laptop problem
An external drive solves storage and creates a dependency. The file you need is on the drive that is at home.
Two honest options. Either accept that the external is a desk-only resource and keep current work internal, or use a small, permanently attached drive. Some people use a low-profile SSD that stays in a port; it works and it occupies a port.
For a laptop, this is the argument for buying more internal storage at purchase even though it is expensive. Storage on a Mac covers sizing at the point of purchase.
External drives need backing up too
The mistake that follows from moving your photo library to an external drive: it is now the only copy, on a single disk, and Time Machine may not be backing it up.
Check Time Machine’s exclusions and make sure the external is included, or back it up separately. A backup plan that survives one thing going wrong covers arranging it.
Questions
Can I run macOS from an external drive? Yes, and it is more fiddly on Apple silicon than it was on Intel. Useful for testing; not a good primary arrangement.
Is an SSD in an enclosure as good as a purpose-built external? Often better, and it depends on the enclosure. A poor bridge chip caps speed and can corrupt data under sustained writes. Buy a reputable enclosure.
Will it wake the drive constantly? Spinning drives spin up when accessed, which is audible and slow. SSDs have no such behaviour, which is another argument for them.
Does an external drive drain the battery? Yes, particularly bus-powered spinning drives. An SSD draws considerably less.