Running Mac OS from a USB drive - a cautionary tale

A few months ago the SSD in my ancient MacBook Air began to falter. The sensor that told my Mac the SSD existed was intermittently failing, so I could use it for a while, then it would freeze as if the system drive had been unplugged.

I wasn’t keen buying a new one until Apple sorted out its keyboard woes, and the prospect of installing a new SSD myself was rather daunting, so my brain came up with what seemed like a brilliant and cheap stop-gap workaround — install the OS onto a USB drive and run the system from that. My thinking (if it can be called that) was that a USB drive is basically a kind of SSD anyway. I knew it would be slower because it would be limited by the speed of the USB bus, but I figured it’d be worth a shot and would keep me going until Apple got its act together.

My idea turned out to be neither brilliant nor cheap. I was able to get it up and running after a lot of futzing about, but I was plagued by spinning beachballs, freezes and random crashes multiple times a day, even when I was running just a text editor. After a month of putting up with that, I ended up ordering a new SSD from for about $150, which is about three times more than I spent on the USB drive, but the SSD was twice as big and, more importantly, actually works. Installing it was a doddle and took no more about twenty minutes.

I’d thought I’d learnt my lesson from past cheapskate shenanigans, but it seems not. On the bright side, it seems that Apple has a new keyboard ready to be introduced sometime next year, so when this MacBook Air finally gives up the ghost, I hope I’ll feel less trepidation about getting a new one.