Extreme SD card, extreme Raspberry Pi performance?

Previously I examined whether the “speed class” of an SD card has a meaningful impact on Raspberry Pi performance. Unsurprisingly, the two classes of SD cards showed very different performance.

But wait…

The good people over at the Raspberry Pi Foundation questioned whether class is the only meaningful metric. Based on their tests, there are variations in brands and other qualities/attributes of SD cards which can have a meaningful impact on Raspberry Pi IO performance. Therefore, I decided to buy a different class 10 card (albeit a better class 10 card) to see how it’s performance might be different from the class 10 card I tested.

The idea

In my previous test I evaluated a Transcend 16GB Class 10 card. Those cards sell for about $12 on Amazon. I decided to test another card, this time a SanDisk 8GB Class 10 Ultra card.

I will admit up front, the SanDisk card is a nicer card based on specs alone. Unlike the Transcend card, the SanDisk card is a “UHS” or “Ultra High Speed” card designed for high speed transfers. The SanDisk is sold as an extreme SD card. This card is also more expensive at $13 for the 8GB model. With that in mind, I wanted to see if, given a budget of ~$12 (which I spent on the Transcend card) this SanDisk card would be worth it.

The test

To benchmark the IO performance, I used Phoronix Test Suite v4.4.1 with the Dbench 4 test. All services which would cause disk performance degradation were stopped. The two units were set up identically (same file system, services, etc.)

The results

As with the last test, these results show a signifiant difference in performance between the two cards. The Transcend had an average transfer rate of 5.75 MB/sec while the SanDisk card had an average rate of 12.56 MB/sec.

Phoronix Test Suite v4.4.1 System Information Hardware: Processor: ARMv6-compatible rev 7 @ 1.00GHz (1 Core), Motherboard: BCM2708, Memory: 470MB, Disk: 8GB SU08G Software: OS: Debian Linux 7.0, Kernel: 3.6.11+ (armv6l), Compiler: GCC 4.6, File-System: ext4, Screen Resolution: 656x416 Dbench 4.0: pts/dbench-1.0.0 [Client Count: 1] Test 1 of 1 Estimated Trial Run Count: 3 Estimated Time To Completion: 37 Minutes Started Run 1 @ 15:45:47 Started Run 2 @ 15:57:51 Started Run 3 @ 16:09:53 [Std. Dev: 1.44%] Test Results: 12.4025 12.7599 12.5291 Average: 12.56 MB/s


If performance matters, especially for small-scale (very small scale) server applications or other IO-intensive tasks, than getting a smaller but higher-performance SD card may be the best cost-benefit decision.