How does SD card storage work?

How does SD card storage work?

One of the accusations often levelled against smartphone manufacturers is that available device storage is never enough.

A 32GB or 64GB handset might sound large, when you consider 1990s floppy discs held just 1.44MB of data.

Yet in today’s multimedia age, when a single photo or MP3 can occupy the equivalent of several floppy discs, it’s easy to fill available space on a smartphone’s hard drive.

We say ‘available space’ because a significant percentage of phone storage is filled with an operating system and pre-installed software.

Much of this is manufacturer-specific bloatware which can’t be deleted.

Consequently, phones may begin reporting low storage after a matter of months, necessitating difficult decisions about what to erase and what to retain.

That is, unless your chosen handset offers SD card storage…

Storage hunters

SD card storage is a form of flash memory whose lack of moving parts makes it incredibly stable, suitable for long-term use without corrupting or wearing out.

SD’s origins date back to 1999, when Panasonic, SanDisk and Toshiba jointly unveiled a global standard for portable storage media known as Secure Digital.

These cards were originally designed for the burgeoning digital camera market, though their subsequent metamorphosis into miniSD cards hinted at other potential uses.

Then came the third generation of microSD cards, whose diminutive dimensions were perfect for slotting into a smartphone’s case.

Given the relentless rate of microchip advances, a tiny microSD card could potentially hold 128 terabytes of data.

In reality, most offer storage capacities measured in gigabytes. It’s easy to see how a 64GB smartphone would be transformed by dropping in a 256GB microSD card.

But how does this work in practice?

Slot machines

SD card storage is only available on Android devices, since Apple doesn’t consider it worthy of inclusion on iPhones.

Contemporary handsets with card slots include the Samsung Galaxy S20, the Nokia 7.2 and the LG G8X.

These smartphones treat the microSD card slot rather like a D: drive on a desktop computer.

If there’s a card in the slot, the device will recognise its presence, reading and writing to it at speeds determined by the card’s class.

(This identifies the number of megabytes which can be written to the card per second, with Class 10 currently the fastest mainstream rating).

Files are generally saved to internal storage by default, switching to the SD card if there’s no room left.

Alternatively, the user can instruct particular apps and utilities to save here by default.

A card can be ejected at any time, facilitating data transfers onto other machines without laboriously uploading each file to the cloud or transmitting it along sluggish USB cables.

And while cards have physical write-protection buttons, formatting solid state storage is a quick and painless process.

However, given the storage contained on many microSD cards, formatting may not be necessary for a long time…

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