Updated SD card speed tests
As some of you may know, Jim and I benchmarked a number of SD cards a couple of years ago.
Jim has a blog post here https://mkmakerspace.co.uk/speed-testing-cheap-micro-sd-cards/, and I did 4K block and random tests to establish their suitability as Raspberry Pi boot devices.
Unfortunately the 16GB LD card which was then good value is now rather expensive on AliExpress compared with the competition, so I have been looking for replacements. Several of these arrived recently and are looking like good (and much cheaper) alternatives.
Each card was checked for true capacity using F3probe, and performance tests were then run using udisks for the 10MB block speeds and iozone for the 4K random block speeds.
The results of the tests are shown in the table below. All speed figures are in MB/s.
| Description | Price (12/2019) | 10MB Read | 10MB Write | 4KB Read | 4KB Write |
| LD 32GB | £4.59 | 79 | 20 | 2.3 | 0.7 |
| LD 16GB | £4.23 | 88 | 51 | 2.5 | 1.1 |
| Microdrive 32GB Red | £1.90 | 92 | 40 | 2.6 | 1.2 |
| Microdrive 32GB Blue | £2.02 | 86 | 61 | 2.5 | 1.2 |
| Microdrive 16GB Red | £1.90 | 91 | 40 | 2.6 | 1.4 |
| Microdrive 16GB Blue | £1.80 | 82 | 48 | 2.7 | 1.5 |
These Microdrive cards have much better performance than the one tested two years ago, and for small I/O operations are faster than the LD cards. 32GB is now broadly comparable speed-wise for these cards, and prices are very similar to the 16GB versions.
A more detailed spreadsheet with many more figures can be found here.
