sandisk-ultra-extreme-microsd-32This experiment compares the speed of Sandisk Ultra microSD 32GB vs. Sandisk Extreme microSD 32GB. Sandisk Ultra promises “up to 48 MB/s” speed and Sandisk Extreme promises “up to 60 MB/s”. Both cards are rated as Class 10 and UHS-I enabled. Sandisk Extreme is more expensive than Sandisk Ultra, so let’s see if the price difference is worth the performance difference.

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). 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 Sandisk Ultra
Sandisk Extreme
Samsung Evo
WRITE A 5 mins 20 secs
avg speed 13.60 MB/s
1 mins 23 secs
avg speed 52.43 MB/s
3 mins 24 secs
avg speed 21.33 MB/s
WRITE B 8 mins 15 secs
avg speed 12.02 MB/s
2 mins 3 secs
avg speed 48.37 MB/s
4 mins 20 secs
avg speed 22.88 MB/s
WRITE C 42 mins 13 secs
avg speed 2.21 MB/s
19 mins 0 sec
avg speed 4.91 MB/s
25 mins 15 secs
avg speed 3.70 MB/s
READ A 1 mins 37 secs
avg speed 44.87 MB/s
1 min 37 secs
avg speed 44.87 MB/s
1 min 57 secs
avg speed 37.20 MB/s
READ B 2 mins 27 secs
avg speed 40.47 MB/s
2 mins 26 secs
avg speed 40.75 MB/s
2 mins 34 secs
avg speed 38.63 MB/s
READ C 15 mins 49 secs
avg speed 5.90 MB/s
5 mins 58 secs
avg speed 16.62 MB/s
7 mins 16 secs
avg speed 12.85 MB/s

As expected, Sandisk Extreme wins all tests. To be fair, Samsung Evo is positioned as direct competitor to Sandisk Ultra. Samsung still has Samsung Evo Plus and Pro with higher speed specifications, so this experiment does not show that Samsung memory cards are slower than Sandisk. We need to compare products from the same level to actually compare them.

Usually, copying a lot of small files take significantly longer time because there are additional process that must be completed for each file. However, this experiment shows interesting results as READ A is actually slower than WRITE A and READ B is slower than WRITE B. I can only guess that this is caused by the writing speed of my Mac mini’s internal HDD. With transfer speed reaches a point higher than the writing speed of my HDD, the READ process (which basically read data from micro SD card and write them to my internal storage) got limited by the writing speed of my HDD. If I do this experiment using Macbook Pro with SSD, the results might be different.

Edit 27 Jun 2020: today I repeat this experiment for the Sandisk Ultra and Sandisk Extreme micro SD cards with my Mac mini using SSD, you can see the results here.