Alir
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Class 10 vs Class 4 sd cards

Thu Jul 04, 2013 8:11 pm

Do class 10 sd cards improve performance compared to having a class 4 sd card?
Or is there no difference when using a raspberry pi?

I want to get a class 10 since I'm under the impression the pi would run faster but I would like to know if there is actually any difference?
cheers.

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FTrevorGowen
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Re: Class 10 vs Class 4 sd cards

Thu Jul 04, 2013 8:54 pm

As I understand it the "class" of an SDHC card is mainly an indicator of its "writing speed" ("reading speed" being "much the same" for most "classes"). Hence writes to a class 10 card may be ~10/4 times faster than a class 4 card. From a "system performance" point-of-view it depends on what the system is doing. For example "file uploads" (to a Pi) or O.S upgrades will be slower for a class 4 card because a lot of "writing" is taking place. "File downloads" (from a Pi) and "general program execution" are likely to mainly involve "reading" and thus have little dependance on the class of the card. For more detailed info. see the wiki at http://elinux.org/RPi_SD_cards#SD_card_performance .
Trev.
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

bennettp123
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Re: Class 10 vs Class 4 sd cards

Wed Jul 17, 2013 9:39 am

Alir wrote:I want to get a class 10 since I'm under the impression the pi would run faster but I would like to know if there is actually any difference?
The answer is "Maybe yes, maybe no".

The reason is that SD "class" ratings are determined mostly by measuring large sequential writes, and that is exactly what most SD cards are optimised for. However, most disk operations on a Linux system are small random reads, with some small random writes thrown in for good measure. This kind of performance varies greatly between SD cards of the same class, and may even differ between two identically branded SD cards.

In other words, unless you're using the SD card in a camera, there's no guarantee that a Class 10 will be any faster than a Class 4.

dom
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Re: Class 10 vs Class 4 sd cards

Wed Jul 17, 2013 11:31 am

Alir wrote:Do class 10 sd cards improve performance compared to having a class 4 sd card?
Or is there no difference when using a raspberry pi?
There is a huge difference between using a fast sdcard and a slow one, but as already stated that's only loosely correlated with the class of sdcard.

I've found a class 4 Sandisk booted quicker and was generally more responsive than a no-name class 10.
(although a class 6 or class 10 Sandisk was faster still).

KeremER
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Re: Class 10 vs Class 4 sd cards

Fri Mar 25, 2016 11:23 pm

Although this is an old tread I hope that it would help people to choose a correct sdCard for their installations.

There's a huge difference. The other day I have installed Raspbian over an old Class 4 sdCard and Booted it it took ages to run the apt-get upgrade since it does a great deal of writing. It took nearly 6-8 hours. That's when I decided to move to a Class 10 SdCard this time the same upgrade took less than 30 minutes.

But once it was written and if your setup would not require updates tyou can pick a Class 4 sdCard.

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