Why the internal memory of a smartphone remains better than a microSD card

The mistake

Some people think that buying a mobile with 32 GB of internal memory and then add 32GB via microSD equivalent to buy a smartphone at 64 GB. That's wrong. Add external storage is always cheaper, which is why it is tempting to use this solution. Why? To explain the problem, we will have to take a look on the side of Marshmallow and changes by updating the operating system.

Before Android 6.0 Marshmallow

On devices not running Marshmallow, the type of data that can be stored on a microSD card is different from the internal data of the phone. You can put music, videos and pictures on your card, but it's more complicated with regard to application data. For example, you cannot install an application entirely on the microSD card. You can move some data, but that's all.

This means that even with a microSD card of 128 GB added to 16GB of internal storage, you could quickly find yourself running out of space. It should therefore be aware that the microSD cards are limited in terms of data types, while the internal storage can store any type of data.

After Android 6.0 Marshmallow

Google now offers unify internal storage and microSD via a feature called Scalable Storage (adaptable storage in French). With the latter, you can use a microSD card in the same way that your internal storage. The problem with this method is that it formats the SD card to operate only on the mobile in question and makes it difficult to re-use on another device.

But even so, the behavior of a formatted microSD card will not be the same as that of internal storage. The speed of reading and writing data depends on the type of storage and largely affects system performance.

Traditionally, access to data on an external storage medium has been slower than on the interior. Scalable Storage with functionality, this remains largely true: the unification of the two storage media will affect performance through speed reading and writing.

But to make matters even more complex, performance may also increase in some cases.
On the HTC One A9

On the HTC One A9, a microSD card can actually improve read performance and write device. It depends on the type of SD card, but with a SanDisk Extreme Plus 64GB, speed reading and writing of our One A9 increased. No one really impressive, but enough to be mentioned.

On the Galaxy S7

The Galaxy S7 made things worse yet, because its microSD expansion does not use the Scalable Storage feature Android 6.0 Marshmallow.

In us based on our initial tests, it appears that the microSD expansion Galaxy S7 and S7 edge offers external storage media in the traditional sense (which only supports media files). It is possible to transfer some applications on the supports SD but there is a limit in size.

Conclusion

Android Marshmallow attempted to finally unify the internal storage space and microSD. With Scalable Storage function, it is finally possible to use microSD cards to store all types of files (except on some series such as LG and Samsung).

But for the moment, still I would advise against buying a microSD card if your goal is simply to expand the internal storage. Unless you are on your mobile supports the function Adaptable Storage, and a moderate impact on the performance did not scare you. Also keep in mind that the reliability of microSD cards varies among manufacturers.

If your goal is just to store media without exhausting internal storage, while a microSD is ideal for you. What do you think of microSD extensions? In what case would you recommend its use?