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I have to bought a SD card for my raspberry pi. It is better to have a huge writing speed (like 95 MB/s) or it is not so important and I can buy slower SD (30 MB/s or 45 MB/s) ?

Red
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6 Answers6

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I have to bought a SD card for my raspberry pi. It is better to have a huge writing speed (like 95 MB/s) or it is not so important and I can buy slower SD (30 MB/s or 45 MB/s) ?

No matter what, you will not much exceed 20 MB/s (read or write) on the pi's SD card bus. Have a look at the chart here, and notice the very fastest write speeds are 21 or 22 MB/s. I've done my own test of class 4 vs. class 10 -- notice they had identical read speeds of ~20 MB/s indicating both cards were limited by the pi's SD card bus.

Subsequent to that, I got a Sandisk class 10, and it far out performs the (disappointing) write speed of the Adata class 10. Moral: don't buy a cheap class 10 card just to have a class 10 card.

This doesn't mean a class 4 is just as good as a class 10, either -- but you can read that chart yourself.

Community
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goldilocks
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It is not necessary to have the fastest writing speed.

A class 10 would only be advantageous if you wish to write a lot of video from the camera.

For most use a class 4 or 6 is perfectly adequate. You won't notice the difference when using the RPi for most normal applications.

Chenmunka
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I would go with a cheap SD card and make a USB (3.0) setup. It's faster and you can overclock the system. and a 16 GB USB 3.0 is also cheaper than a class 10 SD.

The rasp only has USB 2.0 ports, but USB 3.0 sticks are faster internally, so they will be overall faster also on a 2.0 USB port.

Greenonline
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user2452250
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I have two Kingston 16GB memory cards, a class 4 & a class 10, otherwise identical.

I tested both, measuring boot time, using exactly the same version of Rasperian (Nov 2016) on identical Raspberry Pi's side by side.

The class 10 boots up in: 22 seconds.
The class 4 boots up in: 80 seconds.

So class 10 massively out performs the class 4, in my testing.

Mtl Dev
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It depends on your application. If you need a lot of space for your application, get a class 4 SD. They're cheaper. However, if you're doing something like a media center where read speeds are important and you're using an external drive for storage, get a small(2GB or 4GB) class 10.

billkd
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One thing to consider is also the write and especially read-speed on small files!

Sadly class 10, 4, etc. or even the maximum write speeds like 45 MB/s or 90 MB/s are no indication whatsoever for that. It really makes a difference in performance though (in general operating system speed for example).

Unless you are just handling "big" files, like it being a FTP-Server with only video files (which also most likely would have the network speed as bottleneck), not using the card that much at all, or when you have a lot of CPU heavy tasks and the processor is the main bottleneck instead.

Edit: Here is a nice list of benchmarked cards

Levite
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