Tardisk: Boost internal MacBook storage – externally

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Tardisk Pear


Boosting internal MacBook storage – externally
Apple’s habit of making its Macs ever more impervious to upgrading has become a topic of widespread scorn in recent years, with the company’s use of proprietary ‘pentalope’ screws, superglued-in batteries and soldered-down RAM chips coming in for a lot of criticism from veteran tinkerers.

One component that has so far escaped Apple’s anti-upgrade sealant treatment however is the solid-state storage of Retina MacBook Airs and MacBook Pros (though not Retina MacBooks – a bleak sign of things to come perhaps).

Sadly, installing a new internal SSD into one of these machines isn’t a matter of wacking in any old memory module – certain Mac models only work with certain types of flash chip so you do have to know what you’re looking for. And as you would expect, the more recent the Mac, the more expensive the memory.

Of course, the easiest way to avoid having to upgrade the internals is to get an external drive – or buy a Mac with adequate storage in the first place.

The problems with the first solution are that it takes out one of your USB ports, it’s another piece of kit to carry around and it’s very unlikely to match the speed of your internal SSD; as for the second solution… well, it’s likely just too damn late for that. So is there an alternative to biting the bullet, opening up your Mac and potentially voiding the warranty?

The SDXC card slot

The SD card slot in MacBook Airs and Retina MacBook Pros has gained popularity over the last couple of years as a convenient solution for extending storage capacity (alas, the 12-inch MacBook lacks a card slot) and a number of third-party manufacturers offer dedicated expansion drives for this purpose.


While standard SD cards suffer the indignity of protruding from the unibody casing leaving them prone to damage and generally just looking a bit naff, cards like the Transcend JetDrive Lite sit flush with the case edge while leaving just enough of a gap to allow them to be removed.

By using high-class multi-level cell (MLC) flash memory, these purpose-made modules typically offer higher speeds than cheaper camera SD cards (the JetDrive promises 90MB/s read and 60MB/s write for instance) but they still fall short of the kind of transfer rates internal SSDs consistently rack up.

The only exception to this rule that I know of is the Tardisk Pear, billed as the ‘first ever plug-and-play Hybrid drive’, and I recently got my hands on one.


The Tardisk Pear comes in 128GB ($149/£97/€132) and 256GB ($400/£259/€353) capacities, and like its competitors slides seamlessly into your empty SDXC slot and mounts on your desktop just like an external hard drive. However the similarities end there, because the Tardisk has a trick up its sleeve that I’ve not seen in any other product of this kind.

Insert Tardisk

The ‘Pear’ in the name refers to the Tardisk’s (reversible) ability to pair with your internal SSD drive and create a single unified volume, so that in my own test a 256GB system volume was doubled in size to 512GB in a matter of seconds. The Tardisk achieves this with an ingenious piece of software that leverages Apple’s Core Storage layer, the same logical volume format that underlies the company’s Fusion Drive technology.

Fusion Drive

Briefly, Apple’s Fusion Drives use a hybrid implementation of Core Storage to merge a traditional platter hard disk drive with a smaller-sized SSD and present it to the operating system as a single logical volume. The OS then manages the drive so that the most frequently accessed data is stored on the faster SSD while infrequently used items are kept on the hard drive, resulting in faster access times overall.

What the Harvard folks behind the Tardisk have done is rework this hybrid tech to maintain a cache on the internal SDD so that once paired, disk performance is maintained – and in my experience even slightly improved, if only marginally. A Blackmagic Disk 5GB Speed test confirmed this by returning post-Pear scores that were consistently 5-10MB/s faster than my non-paired SSD results.

BlackMagic Speed Test

This performance will no doubt be helped by the Tardisk’s UHS-1 speed Class-3 flash memory controller (UHS-1 is the official speed requirement for shooting 4K video), but given that UHS-I has a maximum bus interface speed of 104 MB/s there is clearly more going on behind the scenes.

Indeed, using the module as a standard separate volume returns read/write scores in the 85-90MB/s range for the same test, which for an SDXC card is nothing to be sniffed at, but it does bring me to an issue regarding the card’s compatibility, at least for my own setup.

Tardisk Pear installer

Sadly, the Tardisk pairing process refused to complete on first try because my system drive was divided into multiple partitions. I had to temporarily remove my Boot Camp volume (which is crucial to my work) and resize the SSD into a single partition before I could get it to play nice.

The team behind the device told me that this single partition limitation was a conscious decision in order to remove a layer of complexity from the setup process, and also to decrease the chance of something going wrong with the Windows/Core Storage file management systems. However it’s not impossible in principle and it’s something they are working to bring to the next version.

As it is, I’m currently using the Tardisk as a separate on-board Time Machine drive (Dr Who fans take note!) and that’s been working just as seamlessly, so much so in fact that I often forget it’s there working away in the background, silently backing up my files wherever I go.

The Tardisk Pear chip-integrated microSD card will be available in 128GB and 256GB capacities for a variety of MacBook Pro and MacBook Air models, and can be ordered directly from Tardisk.com from Thursday 29th October.