A quick and simple way to add up to 128GB of storage to a MacBook

The other week, I commemorated my 75 days of owning a MacBook Pro by giving you a look at how I transformed the shiny slab of aluminum and glass into a system capable of doing serious work.

In that post I noted that I'd augmented the meagre 256GB SSD with a 32GB SanDisk Cruzer Fit drive. This is a low-profile drive that's not much bigger than a fingernail that fits unobtrusively into the USB port and allows me a place to store data that would otherwise clutter up my already cramped internal drive.

See also: 75 days with a MacBook Pro

This isn't a perfect solution. First off, it's slow, averaging read speeds of only about 20MB/s and write speeds of around about 5MB/s.

Not great. In fact, if I'm being honest, it's rather frustrating. The Cruzer Fit is a great drive, but it's not built for this kind of job. 

SanDisk does make faster flash drives that make use of USB 3.0 and capable of read speeds as high as 190MB/s, but these are much bulkier and not the sort of thing I want sticking out of a USB port all the time.

Another problem is that the largest Cruzer Fit drive that SanDisk makes is the 32GB, which is somewhat limiting. Ideally I'd like something small, fast, and with much greater storage.

Then I got an email from Luke. He's a regular reader of this column, and he offered a different take on storage expansion.

His idea was to make use of the MacBook's USB 3.0 enabled SDXC card slot to expand storage. This solution ticks a number of boxes. It supports transfer rates of up to 100MB/s, making it much faster than a USB 2.0 flash drive, and SD cards are small, and yet offer capacities up to 128GB — which is half the capacity of my MacBook's internal SSD.

I also free up a USB port in the process.

All that's left to do is pick the right card based on speed and capacity. Being an avid photographer, I have a number of SD cards lying around, so I tested a few. If you want a good balance of speed and capacity, I suggest you look at the SanDisk Extreme range of cards. These come in sizes ranging from 4GB all the way up to 128GB. They offer a theoretical transfer rate of 45MB/s, with real-world tests showing read and write speeds in the region of 35MB/s. This is nowhere near the 500MB/s I get from the internal drive, but it is nonetheless a workable solution.

Another option is SanDisk's Extreme Pro SD cards. These offer much faster transfer rates (theoretically up to 95MB/s, but in reality read and write rates seem to be in the region of 80 to 85MB/s), but the trade-off is that capacities only go as high as 64GB, and you do pay a premium for the speed. A 64GB Extreme Pro card will set you back around $140.

But you do get a quality card. As I said, I'm an avid photographer, and I have tried SD and CF cards from dozens of companies, but I keep coming back to SanDisk because of the speed and reliability they offer. I could buy cheaper, but I can't buy better.

There is one drawback to using the MacBook's SDXC card slot for external storage, and that's the fact that the card sticks out a fair bit when inserted into the card reader. I wish the card would stick into the slot a little more, but I suppose the slot has been designed to make inserting and removing the card easier, and not to use it as a  permanent expansion.

That said, it's a great solution for those looking for a bit more storage for their MacBook or, for that matter, any notebook or tablet featuring a high-speed SD card slot.