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All about SD Cards

(Topic created on: 04-12-2019 07:53 PM)
Samsung Members Star ★★★

We've decided to make a special post about SD cards. You'll be able to avoid counterfeit SD cards and identify the best card for your device.




Let’s take a look at the different technical specifications that SD cards bear. To do so, please have a look at the image below to identify the different logos most cards possess. 

SD Infographiqe 1-EN.png

Now, let’s see what each of these means:



This class guarantees you that the card will always have a minimal writing speed. This class, which was introduced in the version 5.0 of the SDXC format standard, is set to replace the UHS Speed Class. The possible classes vary between V6 and V90. Each unit is equal to 1MB/s. This means that the card taken in example here has a minimal writing speed of 30MB/s.

It is recommended for 4K recording to use a card with at least a V10 rating. If you use enhanced recording features like 60 fps recording or HDR, at least V30 is recommended. Going beyond 4K, 8K requires at least a V60 card.

This rating also applies to other writing tasks, like copying files on the card.



As of time of writing, no consumer smartphone supports anything higher than UHS-I. It is thus not necessary to worry about this. Do make sure you are not buying a UHS-II card or better, as they are more expensive but you will not be able to enjoy its faster speeds. Other bus versions include UHS-III and SD Express, the latter of which supports NVMe and PCIe.



Prior to version 5.0 of the SD format standard, it was the only high-speed class rating available. As the Video Speed Class, this rating guarantees a minimal writing speed at all times. Possible ratings are U1 and U3. Each unit equals 10MB/s. Thus, the card that was shown precedingly supports a minimum writing speed of 30MB/s.

Between this class and the Video Speed Class, the highest of both classes prevails. So, an U3 and V60-rated card will have a minimal writing speed of 60MB/s.




This rating guarantees a minimal I/O performance for the card. As the name implies, it is very useful for apps that solicit the SD card or are installed on it. It is also useful when reading/writing many small files. This rating guarantees a minimum of reading and writing operations per second (IOPS). There are three possible ratings: A1, A2 and no rating. Higher is better unless you do not plan on having app activity on the card.



Some cards may have another rating on them. It’s the Speed Class. It’s logo is a C with a number inside it. This class was deprecated in favor of the UHS Speed Class. This class also guarantees a minimal writing speed.



There are many kinds of SD cards on the market. It may seem impossible to take the right one, but the following section should greatly help in this endeavor.


We’ll go briefly over Endurance cards. They are made to be continuously used in 24/7/365 scenarios. These are excellent for surveillance cameras or for dash cams. They are slower than normal cards but they are much more durable.

The card’s packaging will show you the card’s peak speeds. They are not sustained but are still useful to consider. Reading speeds are fairly consistent.


Higher-end cards are more durable, are faster, can sustain higher speeds longer and have enhanced warranties. It is important to take it into account, especially if you plan to use the card in the long-term.


As for storage, it depends on how you plan to use the storage. Storing freshly-captured memories and then transfer them to your computer/cloud storage later? Smaller storage such as 64GB will be more than enough. Going in vacation with no way to offload your pictures? Or wanting to have something to watch during the commute to your vacation? 128GB and beyond should be good.


Other use-case scenarios where some cards are more suited include:

Gaming (Switch or mobile games installed on SD)- Favor very high reading speeds and A2 Application Performance Class ratings.

Very high-quality movies/shows stored on the card- At least U1 and high reading speeds.

Recording 4K videos- Privilege V30 cards.

Here’s a breakdown of the 3 biggest SD Card makers’ product ranges:



Ultra- Low-end

Extreme- Midrange

Extreme PLUS- Midrange

Extreme PRO- High-end

Endurance PRO- Endurance card.



EVO - Low-end

EVO Select- Midrange

Evo Plus- High-end.

PRO Endurance- Endurance card.



Lexar uses colour codes instead of names to differenciate their products.

Blue cards- Low-end

Brown- Midrange

White+Gold- High-end

Black+Gold and Platinum- Ultra high-end


beware the knockoffs!

It can be very tempting to try to save big on SD cards. After all, the card previously shown is listed at 210£/120$ USD. It’s not exactly affordable for everyone. But beware of the knockoffs! They are everywhere. These cards are not only slower and less durable, they also have a much smaller capacity than advertised.


What does that mean? Well, picture yourself trying to draw something with a pen. Without real capacity, it’s like you are waving your pen in the air and pretend to be writing. Nothing will be written. And when you’ll try to read the data you have written nowhere… you can see for yourself what happens:



Data lost that way cannot be recovered in any way. To avoid this from happening, make sure to not buy a counterfeit SD Card.



But now you wonder “How am I supposed to avoid them?”. Here’s how:


First, there’s no such thing as the ultimate deal. If you encounter a cheap 1024GB card cheaper than the 64GB card you saw in store, something is fishy.


Then, make a bit of research about the card’s manufacturer. Saw a great deal for a cheap Huawei SD card? Watch out, Huawei does not make SD cards.


The card looks suspiciously like another manufacturer’s design? You are right to be suspicious.


Saw a nice, self-proclaimed “Genuine” SD card but without any mention of the manufacturer? Definitely not a genuine card.


The card’s multiple logos and text to not have the same font? You guessed it, fake as well.


The card does not use the official class logos or even the real SD/SDHC/SDXC logos? Fake too. 


See this card for example. This card costs 6 £. Nice deal for 256GB right? Wrong. No manufacturer, no official logos, fonts are all over the place… User reviews for this listing are unanimous: the real capacity is much smaller than stated, and data stored on the card was lost.



Refrain from buying from AliExpress, Wish, Geek and other self-proclaimed cheap tech platforms. They only sell knockoffs. And nothing else. This time, they even straight up steal genuine companies’ names and design. The card’s quality will not be any better.


The fool-proof way to avoid knockoffs is to buy in stores. Yes, it is more expensive. Yes, the choice is more limited.


However, you are guaranteed to not get any knockoffs. Peace of mind. Otherwise, you can buy from Amazon for example, but make sure to only buy “Ships from and sold by Amazon” cards. The probability of getting a fake card drops drastically. Otherwise, buy cards “fulfilled by Amazon”. They might still be fake, but in the event that you do get a fake card, Amazon will fully refund you.


Amazon is mentioned here only as an example. Do not hesitate to buy from your favourite online retailer/store, but please consult said retailer’s policy on counterfeit/malfunctioning products.



Got an SD card and are anxious to know if it’s not fake? Use a storage testing software like H2testw, available on PCs. If the actual storage space is smaller than claimed, the software will tell you.


Written by CHMultimedia, Level 5 Expert, 

With the collaboration of Cassidy007, Superuser.  revised By  @AntS Moderator

Original article idea by Cassidy, regular Samsung product user.

Create for Samsung Members


Printable version :!AtVm1GOj5C5ExAG5aphtm7ubT-1Z



We hope this is helping you, If you have questions, @CHMultimedia will be happy to answer you


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Extremely useful. Thanks @Cassidy007!

Samsung Members Star ★★

Just come across this,  very informative and beneficial  @Cassidy007 :smiling-face:       Certainly best to avoid pitfalls and false economy.

I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.

First Poster

great job


Just want to add my suggestions if you're not using your phone's internal storage fully or have almost 50+% storage left then please don't use sd card as it'll slow down your phone's performance while loading the files. Also try to install apps on the internal memory always.

However, these days SD Cards are really fast but it's still useless to extend the memory if you'll never use it.

Samsung Members Star ★★

@Garv  Yes I agree with that point if internal storage is not fully  utilised.     Running Apps on SD cards will certainly be slower, see more here 

I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.

First Poster

If I go on

A class 1 (A1) card is specified by 1500 IOPs minimum random read and 500 IOPs minimum random write

A class 2 (A2) card is pecified by 4000 IOPs minimum random read and 2000 IOPs minimum random write

I started with a 128gb Evo Plus (white) but I am totally confused by the A2 rating due to what even a generic A1 from mymemory can provide.

Here is the 32gb Mymemory generic A1
SEQ 4KiB (Q= 8, T= 1): 11.049 MB/s [ 2697.5 IOPS] < 2961.29 us>
SEQ 4KiB (Q= 1, T= 1): 9.881 MB/s [ 2412.4 IOPS] < 413.64 us>
RND 4KiB (Q= 32, T= 1): 7.464 MB/s [ 1822.3 IOPS] < 17518.72 us>
RND 4KiB (Q= 1, T= 1): 6.534 MB/s [ 1595.2 IOPS] < 625.05 us>

SEQ 4KiB (Q= 8, T= 1): 4.771 MB/s [ 1164.8 IOPS] < 6855.69 us>
SEQ 4KiB (Q= 1, T= 1): 4.964 MB/s [ 1211.9 IOPS] < 824.34 us>
RND 4KiB (Q= 32, T= 1): 4.675 MB/s [ 1141.4 IOPS] < 27938.02 us>
RND 4KiB (Q= 1, T= 1): 3.966 MB/s [ 968.3 IOPS] < 1030.37 us>

Here is a EvoPlus 128gb (white) A2

SEQ 4KiB (Q= 8, T= 1): 13.969 MB/s [ 3410.4 IOPS] < 2326.91 us>
SEQ 4KiB (Q= 1, T= 1): 12.428 MB/s [ 3034.2 IOPS] < 329.03 us>
RND 4KiB (Q= 32, T= 1): 11.271 MB/s [ 2751.7 IOPS] < 11601.40 us>
RND 4KiB (Q= 1, T= 1): 10.004 MB/s [ 2442.4 IOPS] < 408.77 us>

SEQ 4KiB (Q= 8, T= 1): 3.386 MB/s [ 826.7 IOPS] < 9657.65 us>
SEQ 4KiB (Q= 1, T= 1): 3.272 MB/s [ 798.8 IOPS] < 1248.77 us>
RND 4KiB (Q= 32, T= 1): 3.508 MB/s [ 856.4 IOPS] < 37161.91 us>
RND 4KiB (Q= 1, T= 1): 3.205 MB/s [ 782.5 IOPS] < 1274.52 us>

Not only does it not meet A2 spec its considerably slower on random writes than a A1 card?
So that got me thinking maybe this card isn't bonfied and I purchased a EvoProPlus 128gb that comes with a samsung usb 3.0 card reader.

Here is a EvoProPlus 128gb (blue) A2

SEQ 4KiB (Q= 8, T= 1): 13.458 MB/s [ 3285.6 IOPS] < 2431.09 us>
SEQ 4KiB (Q= 1, T= 1): 11.470 MB/s [ 2800.3 IOPS] < 356.44 us>
RND 4KiB (Q= 32, T= 1): 10.843 MB/s [ 2647.2 IOPS] < 12041.19 us>
RND 4KiB (Q= 1, T= 1): 10.640 MB/s [ 2597.7 IOPS] < 384.47 us>

SEQ 4KiB (Q= 8, T= 1): 3.261 MB/s [ 796.1 IOPS] < 10015.06 us>
SEQ 4KiB (Q= 1, T= 1): 3.081 MB/s [ 752.2 IOPS] < 1326.09 us>
RND 4KiB (Q= 32, T= 1): 3.172 MB/s [ 774.4 IOPS] < 41072.57 us>
RND 4KiB (Q= 1, T= 1): 3.137 MB/s [ 765.9 IOPS] < 1301.98 us>

Neither of the cards seem to meet A2 specs but I am even more confused for random writes they are even slower than a generic A1!?

The above was used the samsung supplied with the evo pro card reader windows 10 usb3
Am I doing something wrong with the format of these cards as I am totally confused at the results I seem to be getting.
Surely an A2 card for random writes can not be considerabilly slower than an A1 card?

First Poster
Unsupported SD card
This device doesn't support this SD card. Tap to
set up in a supported format.

I have tried many different options to format this SD card, but it fails. I bought a 512GB SD Memory Card from Samsung on Amazon almost a year ago, and when I was transferring a video, a notification appeared on my Note20 ultra5G. We have stopped the work. An error happened. Please back up your data. Now, it is turned into a raw format. Any help is appreciated. thank you
Samsung Members Star ★★★

Hi @NasaDeeJay 

Cqan you give us the Amazon link please ?

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