SD card speed

MartinGH1369

Hello.
Not sure this is in the right place, if not, I am sorry.

I bought a pre-owned Samsung SD card from these forums. I have the SD card in my galaxy s10 .
I used an app (SD card test) to test the card and I'm not getting anywhere close to the advertised speeds of 100MB/s. I am getting around 48MB/s.

The card: https://www.amazon.co.uk/Samsung-Mobile-UK-MicroSD-Adapter/dp/B06XFHQGB9/ref=sr_1_2?keywords=Samsung 128gb SDXC&qid=1553600616&s=gateway&sr=8-2&tag=av0c-21

I had a quick check on YouTube for videos on how to identify a fake and this card doesn't seem to have any of the tell tale signs so I'm wondering if 1. The fakers have upped their game 2. Do SD cards get slower with age?
Anything else it might be?

EndlessWaves

Are you testing the same type of file manipulation the manufacturer is advertising that speed for?

And are you testing on a device capable of the 100MB/s? The card reader may not be capable of 100MB/s.

MartinGH1369

The SD card is in my S10 .
The app is definitely capable as it reads the internal memory at 200MB/s
I'm not sure if I'm testing correctly.
I am using an android app called SD card test pro.

EndlessWaves

The play store description for that SD Card Test pro tells you very little about what it's actually testing, but judging from the settings in the screenshots it's likely to be some sort of sequential transfer speed test, defaulting to a write test.

Notebookcheck's 256kb sequential transfer speed test found the S10 's SD card reader wrote at 60MB/s and read at 70MB/s
Samsung Galaxy S10  Smartphone Review

48MB/s from a generic test on a phone that a respected review site benchmarked at 60MB/s sounds pretty reasonable to me.

I don't know if flash storage slows down significantly with age, but there are usage-related various factors that can affect performance such as how full it is.

There wouldn't be much point making a fake that's almost as fast and has just as much capacity as the real thing as the fakers wouldn't be making much profit. They'd make just as much selling as their own brand without the risk.

MartinGH1369

The card is completely empty.
What you've said makes sense it just seems like a large difference,  41-48 (the average speed I see with this card) is a lot lower than 60MB/s and that is a lot lower than 100 MB/s.
For reference I tested this card (as it's the only other SD card I have) https://www.amazon.co.uk/Toshiba-Exceria-M302-Micro-Memory/dp/B01EAKAW44/ref=redir_mobile_desktop?_encoding=UTF8&psc=1&ref=ppx_pop_dt_b_pd_title
I was getting between 75 and 81 MB/s.