SD Card differences

[ovadaflame]

I've ran a hefty benchmark twice on the same Raspberry Pi, with two different SD cards. One was a 8Gb class 2 SDHC card, and the other was a 8Gb class 10 SDHC UH-1 card. Counter-intuitively, the benchmark ran from the class 2 card ran significantly faster in the majority of the individual benchmark processes. How is this possible? Perhaps the class 10 is so fast the processor has to divert more attention to the card instead of the benchmark?

*Note: the cards were clones of the exact same system w/ the exact same coding, the only difference between the two runs was the SD card type.

[GTR2Fan]

I think you mean 8GB.

It depends what kind of benchmark it was. If it was predominantly small writes then it's not uncommon for a lower class rated card to knock spots off a higher class rated card. Both of my big-name 32GB Class 10 SDHC cards are snails in that respect compared to my no-name Class 4 and Class 6 cards.

[ragnarjensen]

Speed classes 2, 4, and 6 assert that the card supports the respective number of megabytes per second as a minimum sustained write speed for a card in a fragmented state. Class 10 asserts that the card supports 10 MB/s as a minimum non-fragmented sequential write speed and uses a High-speed bus mode

Class 10 is geared at Full-HD video recording on a freshly formatted card. Just a few but very big files.
They can struggle if you have many small files in a fragmented file system.

--
Ragnar

[ovadaflame]

GB.. yes yes...
The benchmark was processing heavy, not read/write heavy, calculating long form algorithms returning MFLOPS..
BUT that makes sense, class 10 being geared for few but big files vs the other.. Thanks!