Not all memory cards are created equal, even those with the same brand. I had Samsung Evo microSD 16 and 64GB for a while and was curious whether these cards from the same brand and type (but different capacity) deliver the same performance or not. I did a quick test and discovered that sometimes their speed can be noticeably different. So I bought Samsung Evo microSD 32 GB to complete my experiment.
For this test, I use a Mac mini with built-in USB 3.0 ports. The memory cards are accessed through a USB 3.0 memory card reader (Transcend RDF5). Samsung Evo microSD cards are rated as Class 10 and UHS-I enabled with promised speed “up to 48 MB/s”. Theoretically, these three memory cards should have similar performance.
I prepared three sets of data to be written to, and read from the micro SD cards:
- Data A is 1 large file. The size is 4.25 GB.
- Data B is a set of 12 medium files. The total size is 5.81 GB.
- Data C is a set of 45,976 small files. The total size is 5.47 GB.
Testing process is simple. First I formatted each memory card using ExFAT so at the beginning of the test, they are empty. The formatting uses standard ExFAT from Windows with all default settings. To measure WRITE speed, I copied each set of data into each memory card and timed the process. To measure READ speed, I copied back those sets of data back into my computer and timed the process. To perform the file transfers, I use a tool named ChronoSync 4.6.2. This is a backup app for Mac, but I have good experience using it as file copier because it performs generally faster than using the standard Finder.
| Operation | Data | Evo 16 GB |
Evo 32 GB |
Evo 64 GB |
| WRITE | A | 5 mins 20 secs avg speed 13.60 MB/s |
3 mins 24 secs avg speed 21.33 MB/s |
3 mins 4 secs avg speed 23.65 MB/s |
| WRITE | B | 7 mins 30 secs avg speed 13.22 MB/s |
4 mins 20 secs avg speed 22.88 MB/s |
4 mins 20 secs avg speed 22.88 MB/s |
| WRITE | C | 34 mins 30 secs avg speed 2.71 MB/s |
25 mins 15 secs avg speed 3.70 MB/s |
28 mins 6 secs avg speed 3.32 MB/s |
| READ | A | 1 mins 49 secs avg speed 39.93 MB/s |
1 min 57 secs avg speed 37.20 MB/s |
1 mins 45 secs avg speed 41.45 MB/s |
| READ | B | 2 mins 20 secs avg speed 42.49 MB/s |
2 mins 34 secs avg speed 38.63 MB/s |
2 mins 12 secs avg speed 45.07 MB/s |
| READ | C | 10 mins 53 secs avg speed 8.58 MB/s |
7 mins 16 secs avg speed 12.85 MB/s |
10 mins 42 secs avg speed 8.72 MB/s |
As expected, copying a lot of small files take significantly longer time because there are additional process that must be completed for each file. READ operations are always faster than WRITE operations for the same set of data. The 16 GB card performs slower every test, with WRITE C experiment showing the most noticeable difference. The highest speed of 45.07 MB/s is reached by 64 GB card for reading Data B, reasonably close to the promised 48 MB/s.
It is worth to mention that somehow the 32 GB card I just purchased has slightly different color compared to the 16GB and 64 GB cards. I am not sure why. All cards were purchased from trustable source and I would like the believe that they are all genuine. So perhaps just different batch or Samsung made minor design change.
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