Fast microSD Cards for Raspberry make the difference.

microSD Card Benchmarks

In my experience, one of the highest-impact upgrades you can perform is to buy the fastest possible microSD card—especially for applications where you need to do a lot of random reads and writes.

There is an order-of-magnitude difference between most cheap cards and the slightly-more-expensive ones (even if both are rated as being in the same class)—especially in small-block random I/O performance. As an example, if you use a normal, cheap microSD card for your database server, normal database operations can literally be 100x slower than if you used a standard microSD card.

Because of this, I went and purchased over a dozen different cards and have been putting them through their paces. Here are the results of those efforts, in a nice tabular format:

Raspberry Pi model 2 B

Card Make/Model hdparm buffered dd write 4K rand read 4K rand write
OWC Envoy SSD (USB) 64GB 34.13 MB/s 34.4 MB/s 7.06 MB/s 8.20 MB/s
SanDisk Ultra Fit (USB) 32GB 31.72 MB/s 14.5 MB/s 4.99 MB/s 1.07 MB/s
Samsung Pro+ 32GB 21.75 MB/s 18.7 MB/s 8.31 MB/s 1.75 MB/s
Samsung Pro 16GB 18.39 MB/s 18.2 MB/s 7.66 MB/s 1.01 MB/s
Samsung Evo+ 32GB 18.45 MB/s 14.0 MB/s 8.02 MB/s 3.00 MB/s
Samsung Evo 16GB 17.39 MB/s 10.4 MB/s 5.36 MB/s 1.05 MB/s
SanDisk Extreme Pro 8GB 18.43 MB/s 17.6 MB/s 7.52 MB/s 1.18 MB/s
SanDisk Extreme 16GB 18.51 MB/s 18.3 MB/s 8.10 MB/s 2.30 MB/s
SanDisk Ultra 16GB 17.73 MB/s 7.3 MB/s 5.34 MB/s 1.52 MB/s
NOOBS (1.4, C6) 8GB 17.62 MB/s 6.5 MB/s 5.63 MB/s 1.01 MB/s
Transcend Premium 300x 32GB 18.14 MB/s 10.3 MB/s 5.21 MB/s 0.84 MB/s
PNY Turbo (C10 90MB/s) 16GB 17.46 MB/s TODO 6.25 MB/s 0.62 MB/s
Toshiba (C10 40MB/s) 16GB 17.66 MB/s 11.2 MB/s 5.21 MB/s 0.21 MB/s
Sony (C10 70MB/s) 16GB 15.38 MB/s 8.9 MB/s 2.47 MB/s 0.24 MB/s
Kingston (C10) 16GB 17.78 MB/s 9.0 MB/s 5.75 MB/s 0.21 MB/s
Kingston (C10) 8GB 12.80 MB/s 7.2 MB/s 5.56 MB/s 0.17 MB/s
Nasya (C10) 16GB 16.05 MB/s 8.4 MB/s 2.28 MB/s 0.38 MB/s
No-name (C4) 4GB 13.37 MB/s Sad Painful Excruciating

Raspberry Pi model 3 B

Card Make/Model hdparm buffered dd write 4K rand read 4K rand write
Samsung Pro+ 32GB 21.88 MB/s 20.2 MB/s 9.61 MB/s 2.16 MB/s
Samsung Pro 16GB 21.62 MB/s 22.1 MB/s 9.41 MB/s 1.66 MB/s
Samsung Evo+ 32GB 21.77 MB/s 15.8 MB/s 9.66 MB/s 3.43 MB/s
Samsung Evo 16GB 20.08 MB/s 10.4 MB/s 6.02 MB/s 1.02 MB/s
SanDisk Extreme Pro 8GB 21.02 MB/s 21.2 MB/s 9.07 MB/s 1.25 MB/s
SanDisk Extreme 16GB 22.08 MB/s 21.8 MB/s 9.44 MB/s 2.42 MB/s
SanDisk Ultra 16GB 20.79 MB/s 7.9 MB/s 5.98 MB/s 1.57 MB/s

Raspberry Pi model 3 B results – overclocked microSD

You can double the microSD card reader’s speed by adding an extra dtoverlay configuration inside /boot/config.txt (for instructions, see How to overclock the microSD card reader in the Raspberry Pi 3).

Card Make/Model hdparm buffered dd write 4K rand read 4K rand write
Samsung Pro+ 32GB 39.93 MB/s 31.0 MB/s 12.15 MB/s 1.84 MB/s
Samsung Pro 16GB1 31.59 MB/s 32.8 MB/s 11.20 MB/s 1.48 MB/s
Samsung Evo+ 32GB 37.68 MB/s 20.0 MB/s 12.20 MB/s 3.75 MB/s
Samsung Evo 16GB 32.47 MB/s 11.8 MB/s 6.44 MB/s 1.25 MB/s
SanDisk Extreme Pro 8GB 40.52 MB/s 35.9 MB/s 11.31 MB/s 1.28 MB/s
SanDisk Extreme 16GB 40.88 MB/s 39.1 MB/s 11.77 MB/s 2.36 MB/s
SanDisk Ultra 16GB 37.41 MB/s 8.5 MB/s 6.71 MB/s 1.61 MB/s

1 The Samsung Pro refused to overclock to 100 MHz; I could only overclock at 80 MHz reliably.


All the benchmarks can be run quickly and easily by running a shell script in the Raspberry Pi Dramble repository:

raspberry-pi-dramble/master/setup/benchmarks/ | sudo bash

hdparm buffered

sudo hdparm -t /dev/mmcblk0

Rationale: hdparm gives basic raw throughput stats for buffered reads (by the disk/device itself). You could also test with -T instead of -tto test the OS filesystem cache performance (which allows the OS to dramatically speed up certain read operations), but for our purposes we just want to test the device itself.


  1. Install hdparm: sudo apt-get install -y hdparm

dd write

sudo dd if=/dev/zero of=/home/pi/test bs=8k count=50k 
conv=fsync; sudo rm -f /home/pi/test

Rationale: dd simply copies data from one place (if) to another (of). If your filesystem caches are big enough, this is a pretty poor disk speed comparison test. Because of that, make sure that count is set to a parameter large enough to cause the OS to actually write data to the drive (e.g. 50k 8k blocks ~= 400 MB, which shouldn’t be able to be cached on a microSD card in a Pi!.

iozone 4K Random read/write

iozone -e -I -a -s 100M -r 4k -i 0 -i 1 -i 2 [-f /path/to/file]

Rationale: iozone is a very robust filesystem benchmark tool, which does a lot of useful tests that make sure you’re getting a broad overview of read and write performance for a variety of block sizes and situations. I like the lower block size random I/O tests especially, because many operations (like logging data, writing a row to an ACID-compliant database, or bulk loading of data) require as fast of small-block-size random I/O as possible.

Most cheap microSD cards, even if rated as being 100MB/sec+ class 10 cards, can’t sustain anywhere near that rate when writing random data—especially on the Raspberry Pi’s measly data bus. (Note that most of the above benchmarks, when run on a USB 3.0 card reader on my MacBook Air, show 5, 10, or 15 times greater performance in that environment).


  1. Download the latest version: wget
  2. Expand the tarfile: cat iozone3_434.tar | tar -x
  3. Go into the src folder: cd iozone3_434/src/current
  4. Build the executable: make linux-arm
  5. Symlink the executable into your local bin folder: sudo ln -s /home/pi/iozone_434/src/current/iozone /usr/local/bin/iozone