How do SD cards hold so much data? (ex: 1TB microSD cards)?

So much storage in such a tiny card

we own hundreds of memory cards, external solid state drives, and hard drives, and seeing the storage double and double every few years never gets old.

We take storage for granted nowadays because you can get so much of it on the cheap. But you really appreciate how far storage technology has come if (like me) you grew up when a 2 megabyte memory card was once considered state of the art.

So maybe you can sympathize when I say it moves me to see SanDisk's 1TB microSD card because holy moly it's real. A 1TB microSD card isn't a dream anymore. 

No more lugging around a bulky external hard drive (which is more prone to failure because of its mechanical platter-based design) or even a smaller SSD.

With this micro-sized memory card, I can truly carry all of my essential digital files with me in my wallet (if I wanted to). 

The photo above shows how portable storage has evolved. Ten years ago, 1TB of portable storage was only available in hard drive form. Then about five years ago, portable SSDs became a thing. And earlier this year, Lexar announced a 1TB SD card. SanDisk's 1TB microSD card blows all of them away in terms of storage per volume.

Such tiny size also comes with its own disadvantage: you could easily lose it and — poof — all your data's gone. It's happened to me before. At MWC 2019, I irresponsibly put a nearly full 400GB microSD card in my pocket and somehow lost the dang thing while fishing out change to tip my cab driver. So be careful if you spring for one of these teeny cards.

How much data can you store on a 1TB microSD card?

That's no doubt the first question everyone is going to ask. What on Earth would you need a 1TB microSD card for? If you're asking, you probably don't need it.

But if you'll allow your head to run wild for a little, you can quickly come up with many ways to fill up the memory card. 

It goes without saying, a 1TB microSD card is perfect for digital hoarders who prefer to not delete any files. Like ever.

I've outlined a general overview of how much digital stuff you could store for various common file types:

• About 1,000,000 e-books (at an average size of 1MB per e-book)
• About 200,000 photos (12-megapixel iPhone XS Live Photos at an average size of 5MB) or 500,000 photos (12-megapixel iPhone XS photos at an average size of 2MB)
• About 250,000 iTunes songs (at an average size of 4MB for an average 4-minute tune)
• About 222 Full HD movies from iTunes (at an average of 4.5GB per movie)
• About 41 Blu-Rays (at an average size of 25GB)
• About 31 Nintendo Switch digital games (at a top capacity of 32GB per game; most games that aren't as massive as The Legend of Zelda: Breath of the Wild usually use between 5-10GB of storage, which would work out to about room for 100 to 200 games, respectively)

Of course, few people are likely to use the microSD card for storing one type of file so how much you'll store will vary.

We own several 400GB microSD cards, and they've been valuable for saving high-resolution JPEGs and RAW files simultaneously from my Sony A6300 mirrorless camera. I also use the seemingly excessive storage to save the highest-possible quality 4K videos from the camera. Honestly, I can't remember how I ever lived with a memory card with less storage.

Will it work with my device?

Unfortunately, the answer is maybe. Most Android phones with a memory card slot (even ones from 4-5 years ago) should support this 1TB microSD since they were designed to work with cards with up to a theoretical 2TB of storage (that didn't exist yet). 

However, support will vary based on the device. Some don't work with high-capacity microSD cards. 

I tested the 1TB microSD card in a Galaxy S10+, GoPro Hero 7 Black, Sony A6300 mirrorless camera (within an SD card adapter), and an old LG G5 from 2016 and they all worked fine.

How fast are the read and write speeds?

A ton of storage is mind boggling, but not very useful if it can't read and write data quickly enough.

SanDisk says the 1TB microSD card can achieve read speeds of up to 90MB/s. Running Blackmagic's Disk Speed Test on a 2019 iMac, the results matched the advertised speeds.

According to my Disk Speed Test results, the 1TB microSD card plugged into the iMac (via a generic SD card adapter) was capable of write speeds up to 60MB/s and read speeds up to 90MB/s.

The read and write speeds are slow in comparison to my Samsung T1 SSD, which gets read and write speeds up to 450MB/s over USB 3.0. My 1TB Western Digital My Passport for Mac portable hard drive has faster read and write speeds of 100MB/s and 105MB/s, respectively.

Newer portable SSDs like Samsung's T5 can also achieve read and write speeds up to 540MB/s via USB 3.1 Gen 2 and the Samsung X5 can transfer data at a ludicrous speed of up to 40GB/s over Thunderbolt 3.

Though slower than my portable SSDs, the 1TB microSD wrote about two more megabytes faster than Lexar's 1TB SD card; read speed was the same 90MB/s despite Lexar claiming up to 95MB/s.

However, there is a way to get faster read and write speeds from the 1TB microSD card. Using SanDisk's MobileMate USB 3.0 reader, the Disk Speed Test recorded faster write speeds of about 102MB/s and read speeds of about 160MB/s, which is on par with the reader's advertised "up to 170MB/s" speeds. The downside, of course, is the MobileMate 3.0 reader is sold separately for an extra $13.

Cutting edge comes with a premium cost

Life is good with 1TB of storage in a microSD card. I never worry about running out of storage when I'm shooting photos and videos and never have to downgrade the resolution. I don't bat an eye at game sizes for the Nintendo Switch. And I can backup my personal 256GB MacBook Air to it multiple times.

In a few years, 1TB microSD cards will become the norm. They'll be as common as 200GB and 400GB microSD cards are today that fetch under $100 when they're on sale. But today, SanDisk's Extreme 1TB microSD card is super expensive at $450.

It makes less sense to spend so much money on the 1TB microSD card when Samsung's way faster SSD X5 with 1TB regularly sells for $400. Sure, an SSD is no memory card the size of a fingernail, but it's also not as easy to misplace.

The price will come down. That's just memory cards work. In a year or two, even higher capacity memory cards will make way for price reductions on this little card and then it'll be worth buying. Until then, early adopters with money to burn are likely to be the only ones who'll happily pay for a 1TB microSD card. 

Still, 1TB in a microSD card! Holy shit. What a time to be alive!

Thank YOU!

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