If you're looking to double the storage capacity of a pre-2016 MacBook or MacBook Pro -- and you're not into ripping and replacing your existing drive -- the TarDisk SD expansion card may be for you.
TarDisk has been selling its SD expansion card for several years now. It's up to version 7.0 of its pairing/data migration software.
The TarDisk is a half-length SD card designed to fit flush with your laptop or desktop's SDXC port. It permanently pairs with your MacBook (or MacBook Pro) to seamlessly increase its storage capacity by either 128GB or 256GB.
The TarDisk SD card's capacities mirror those of the base model of MacBook in order to double the system's storage. The SD card is marketed as a simpler way of doubling capacity compared to adding a new SSD to your laptop.
Note: The TarDisk requires an SD card slot, meaning the latest MacBook and MacBook Pro laptops can't use it; they only have USB-C style Thunderbolt 3 ports.
Convenience carries a price premium
The TarDisk pairs (or as TarDisk puts it, "Pears," as in its Pear 2.0 software) with the existing hard drive or SSD, creating a single logical volume that's indistinguishable from your original internal storage device.
The expansion card, however, carries a hefty price: The 128GB version costs about $150 (Amazon price) while the 256GB model goes for about $400 (Amazon price). Any other 128GB SD card with the same performance would run you about 50 cents per gigabyte versus the TarDisk's more than $1 per gig.
For example, Lexar's top-end Professional SDXC card with 128GB costs $68.50 (Amazon price) while a SanDisk Extreme Pro SDXC card costs $64 (Amazon price). Heck, you can even purchase a 512GB SanDisk Extreme Pro SD card for $280 (Amazon price) -- about $120 less than TarDisk's 256GB card.
In fact, I reviewed a PCIe SSD upgrade for my MacBook Pro last year and it was also nearly half the cost of the TarDisk SD card. The OWC Aura PCIe SSDs for MacBook Pro Retina laptops come in 480GB capacity for $348 (retail price) and 1TB capacity for about $428 (retail price).
You can also purchase a complete SSD upgrade kit, which includes the OWC SSD, screwdrivers, a USB standard A to micro B cable and an external PCIe SSD enclosure with USB 3.0 port for $399 (480GB model) or $649 (1TB model).
Ease of installation
So why spend more per gigabyte for the TarDisk card? According to TarDisk, its SD card's software makes it the only MacBook Storage Expansion hybrid drive on the market.
That's "not to mention files being automatically allocated so you can access the files you need securely and quicker than on a traditional external hard drive," a TarDisk spokesperson said.
So basically, it's the ease with which users can double their storage capacity without having to crack open their MacBook, install a fresh version of OS X and migrate existing applications and data to a new SSD. That process can take hours to complete.
Just as the TarDisk virtually meshes with your computer's drive, so does the half-sized SD card fit flush with the laptop's body. A thin, fingernail-sized slot at the top of the SD card allows it to be pulled out if necessary.
After installation, which takes only about 30 seconds, a quick look at "Storage" in the "About This Mac" software will reveal two separate devices, your primary drive and the TarDisk drive. But both icons will now show the total amount of merged storage on your system, and OS X treats both your internal drive and the TarDisk as a single device.
The only discernable difference from upgrading to a higher capacity hard drive or SSD in your MacBook and using the TarDisk is that more frequently used files will reside on the SSD to maintain throughput speeds, while mass storage goes to the SD card.
While simple, TarDisk's installation instructions are a bit intimidating in that they warn the user that once paired with your existing hard drive, it's a permanent upgrade. So, make sure you have a fresh Time Machine backup, in case any data is lost during the pairing process.
But while it's called a permanent upgrade, you can uninstall the TarDisk SD card. The company has a tutorial on its website to unpair the device from your MacBook or MacBook Pro. According to TarDisk, it takes about 20 minutes.
TarDisk instructs users to turn off the Apple's FileVault encryption program while installing the TarDisk device, as it will not be able to copy encrypted files. Installation also requires that you have at least 10% free space on your existing hard drive.
No performance hit
The TarDisk SD card has highly respectable read/write speeds of 95Mbps and 90Mbps, respectively; it's the same as any professional-grade SD card. While that may be fast for an SD card, it's not even in the same universe as a MacBook's internal PCIe SSD, which on my computer comes in around 727Mbps for reads and 680Mbps for writes.
So, why would you ever combine a vastly slower SD card with your hyperfast internal SSD?
According to TarDisk, it gets around the performance disparity by maintaining a cache on the SSD to shift the read/write load.
"This form of cache is commonly used by hybrid mechanical drives with a solid state cache," TarDisk's spokesperson said. "In most cases, the slower component's downsides are negated, but writing and reading large files (a 1080p movie, for instance) to and from the TarDisk can expose the SD card's slower sustained transfer speeds."
After installing the TarDisk device, I ran a performance test using the Blackmagic benchmark software, and there was no change in the read/write speeds of my MacBook Pro.
The choice of either upgrading your drive to a higher capacity SSD or hard drive wouldn't be difficult for yours truly. I'd select the higher capacity SSD every time.
But I can certainly see the case for wanting a fast and simple way to double the capacity on an older MacBook that's accessible to anyone, regardless of their technological prowess. In that case, the TarDisk may be the right choice.