SD card speed


10 posts
by RussABarr » Thu Apr 14, 2016 3:56 pm
I have been trying to determine what micro SD class and speed to use for the operating system that get the maximum performance from the Raspberry model 2 & 3. Since I could not find a good answer I tested several SD cards in both the model 2 and model 3. Below are my results.

________________________________Spec________Windows_____NOOBS Install Speed
Size/Speed__Manufacture___________R/W________R/W Copy_____Pi3______Pi2
32GB/U3------SanDisk Extreme PLUS--95/90 MB/s-----87.5/77.8MB/s--7.8MB/s-----5.7MB/s
16GB/U3------SanDisk Extreme-----------90/40 MB/s-----69.5/49.8MB/s--7.8MB/s-----5.7MB/s
32GB/U1------Transcend 400X------------45/25 MB/s-----85.5/20MB/s-----5.5MB/s-----4.1MB/s
8GB/U1--------Kingston----------------------45/10 MB/s-----43.5/12MB/s-----3.1MB/s-----2.8MB/s
32GB/Class4-SanDisk----------------------16/6 MB/s-------22.5/5.8MB/s----2.6MB/s-----2.3MB/s
8GB/Class4---SanDisk----------------------12/6 MB/s-------22.5/4.5MB/s----2.4MB/s-----2.2MB/s

Note that there is an increase in the Pi performance until the fastest SanDisk Extreme PLUS card.

It is strange that there is no increase in NOOBS install speed when the Windows write speed increased by 50%. The read speed is about the same in the two devices but the write speed increased by more than 50% from 50MB to over 77MB.
I would expect that there would be some improvement in the NOOBS install since most of the SD operations are writes when installing the operating system.

This leads to either the maximum SD interface is limited to about 40MB or NOOBS is not making use of the increase performance. I have not yet written or found a SD benchmark that run on the raspberry so I can measure the actual SD performance.
Last edited by RussABarr on Mon Apr 18, 2016 1:59 pm, edited 3 times in total.
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by pxgator » Fri Apr 15, 2016 5:23 am
So what's all this RPi stuff anyhow? Well folks, it's a feat of engineering from
the UK almost as remarkable as the De Havilland Mosquito and the Colossus.
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by Rive » Fri Apr 15, 2016 5:42 am
This leads to either the maximum SD interface is limited to about 40MB or NOOBS is not making use of the increase performance. I have not yet written or found a SD benchmark that run on the raspberry so I can measure the actual SD performance.


A benchmark software already exists.
http://www.nmacleod.com/public/sdbench.sh

Copy the text then open a terminal and type...
Code: Select all
sudo nano sdbench.sh

...and paste the text in, then save with Ctrl-X, Y, Enter.

Make it executable with...
Code: Select all
sudo chmod +x sdbench.sh

Then run:
Code: Select all
sudo ./sdbench.sh


UHS-1 and HC-1 microsd 32GB or larger 40MB/s are the optimal sdcards for the pi3.

BestBuy sells them for $11 (Samsung EVO+)

To fully utilize the speeds for the card, you have to enable sd_overclock in /boot/config.txt

Code: Select all
dtparam=sd_overclock=100


Image

My Pi3 sd bench results (on the $11 32GB EVO+ Samsung UHS-1/HC-1 micro sdcard as shown above):
Code: Select all
pi@raspberrypi:~ $ sudo ./sdbench.sh

CONFIG:
CLOCK : 100.000 MHz
CORE  : 500 MHz, turbo=1
DATA  : 512 MB, /root/test.dat

HDPARM:
======
 Timing O_DIRECT disk reads: 128 MB in  3.02 seconds =  42.41 MB/sec
 Timing O_DIRECT disk reads: 128 MB in  3.05 seconds =  42.03 MB/sec
 Timing O_DIRECT disk reads: 122 MB in  3.01 seconds =  40.50 MB/sec

WRITE:
=====
536870912 bytes (537 MB) copied, 27.4302 s, 19.6 MB/s
536870912 bytes (537 MB) copied, 27.386 s, 19.6 MB/s
536870912 bytes (537 MB) copied, 25.623 s, 21.0 MB/s

READ:
====
536870912 bytes (537 MB) copied, 12.312 s, 43.6 MB/s
536870912 bytes (537 MB) copied, 12.3474 s, 43.5 MB/s
536870912 bytes (537 MB) copied, 12.3233 s, 43.6 MB/s

RESULT (AVG):
============
Overlay config                      core_freq   turbo   overclock_50    WRITE        READ        HDPARM
                                       500        1     100.000 MHz   19.12 MB/s   41.54 MB/s   41.63 MB/s

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by edo1 » Fri Apr 15, 2016 8:21 am
Rive wrote:To fully utilize the speeds for the card, you have to enable sd_overclock in /boot/config.txt
is it safe? with any card?
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by RussABarr » Mon Apr 18, 2016 2:21 pm
As the Bench mark shows 40MB is about the Maximum transfer speed. Since the maximum read speed of the Samsung U1 is about 48MB this card reaches the maximum transfer rate. The Write spec for this card is about 22MB about half the maximum Pi capacity. The better performing card on write would be the Samsung Pro U3. It has both a read and write speed over the 40MB limit of the Pi.
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by Rive » Mon Apr 18, 2016 2:44 pm
edo1 wrote:
Rive wrote:To fully utilize the speeds for the card, you have to enable sd_overclock in /boot/config.txt
is it safe? with any card?


No. it has to be HC-1/UHS-1 or higher (like what you see here...U with a 1 or higher, or HC-I or higher).

Image
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by mi7chy » Mon Apr 18, 2016 3:26 pm
http://www.pidramble.com/wiki/benchmarks/microsd-cards

I experienced a huge increase in usability going from Sandisk Ultra to Samsung EVO+ which happen to be on sale at Best Buy for $20 for 64GB or $44 for 128GB.
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by edo1 » Mon Apr 18, 2016 8:29 pm
Rive wrote:
edo1 wrote:
Rive wrote:To fully utilize the speeds for the card, you have to enable sd_overclock in /boot/config.txt
is it safe? with any card?


No. it has to be HC-1/UHS-1 or higher (like what you see here...U with a 1 or higher, or HC-I or higher).

so is it safe with any uhs-1 card? (is such frequency covered by uhs-1 specs?)
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by Dis93 » Mon Apr 18, 2016 8:35 pm
I'd say yes, edo1. My PNY UHS-1 card seems fine after the overclock.
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by RussABarr » Tue Apr 19, 2016 1:51 am
Has anyone compared the Samsung Evo+ 128GB/ 64GB to Samsung Evo+ 32GB. If they have the same page size I would expect the 4K write to be the same.
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