Raspberry Pi • View topic

by **semtex** » Wed Mar 14, 2012 12:48 am

I know there are lots of threads asking about which SD cards are more suitable for RasPi, but I haven't found anything that gives a good answer. I looked at the RasPi wiki (http://elinux.org/RPi_Verified.....eripherals) to see some verified SD cards and from there I looked at the benchmark results (http://www.sakoman.com/OMAP/mi.....sults.html) and this is where things got interesting.

SD cards have a class rating that indicates the sequential write speed. So a class 4 card will write at 4MB/s and a class 6 card at 6MB/s. So you might naturally assume the higher the class the better… but not necessarily. SD cards are used in cameras and video cameras where they sequentially read and write large file sizes. But a computer uses random read/write access and the file sizes are typically very much smaller.

The above benchmarks indicate that the SD card is going to have a signficant impact on the overall RasPi performance. For example, one test was to install Gnome r12. The fastest SD card was a Topram 8Gb Class 4 which took 1252 seconds, an average card is the ADATA 8Gb Class 6 card which took 5363 seconds, but the slowest card was an RiData 4Gb Class 6 card which took 15707 seconds… a whopping 12 times slower than the Topram!!

So I wondered if there was a simple, consistent test that could be quickly and easily run on a Windows box that would help everyone identify more suitable cards and maybe this thread could be used as a collection pot for the various results.

The software I used was Crystal Disk Mark (http://crystalmark.info/?lang=en). This performs a sequential test, which is good for cameras and video recorders, but it also does random access tests with record sizes of 512kb and 4kb… which is more like what the RasPi will use.

To kick things off, here are the results for two 16Gb Class 6 SD cards that I have; one from ADATA the other from Lexar.

NOTE: I set the file size to 50Mb, all other settings are default.

ADATA 16Gb Class 6

Lexar 16Gb Class 6

Both cards are the same capacity and class, but look how fast the sequential write speed is of the Lexar compared to the Adata… more than twice as fast! The Lexar is definitely the card I want in my camera.

But now look at the figures for the 512k and 4k tests. The 512k results are similar for both but while the 4k read tests are faster for the Lexar, the 4k write tests for the Lexar are terrible… 5 times slower than the Adata. So maybe the ADATA card is the one I want to use for RasPi?

If others would like to share the performance figures for their SD cards I'm sure there would be some interest.

(Those with experience may like to comment on the real world impact of these numbers).

Thanks

by **xkxx** » Wed Mar 14, 2012 1:40 am

sandisk extreme sdhc 8gb class 10:

           Sequential Read :    21.856 MB/s
Sequential Write :    20.587 MB/s
Random Read 512KB :    21.039 MB/s
Random Write 512KB :     2.114 MB/s
Random Read 4KB (QD=1) :     3.525 MB/s [   860.5 IOPS]
Random Write 4KB (QD=1) :     0.155 MB/s [    37.9 IOPS]
Random Read 4KB (QD=32) :     3.606 MB/s [   880.5 IOPS]
Random Write 4KB (QD=32) :     0.166 MB/s [    40.5 IOPS]

Test : 1000 MB [F: 0.0% (0.0/7572.0 MB)] (x5)
Date : 2011/11/30 18:14:00
OS : Windows 7 Home Premium Edition SP1 [6.1 Build 7601] (x64)

sandisk extreme has the reputation of the only sd card that is suitable for serious server use. if this one doesn't work for raspi i'll definitely yell at someone.

by **rmm200** » Wed Mar 14, 2012 1:53 am

Sandisk Ultra 16GB Micro SDHC Class 6 with adapter, hanging off a hub:

———————————————————————–
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
———————————————————————–
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read :    19.927 MB/s
Sequential Write :    10.215 MB/s
Random Read 512KB :    19.618 MB/s
Random Write 512KB :     3.112 MB/s
Random Read 4KB (QD=1) :     4.026 MB/s [   982.9 IOPS]
Random Write 4KB (QD=1) :     1.695 MB/s [   413.8 IOPS]
Random Read 4KB (QD=32) :     4.046 MB/s [   987.9 IOPS]
Random Write 4KB (QD=32) :     1.368 MB/s [   333.9 IOPS]

Test : 50 MB [H: 0.0% (0.0/14.8 GB)] (x5)
Date : 2012/03/13 19:13:34
OS : Windows Vista Ultimate Edition SP2 [6.0 Build 6002] (x64)

Very happy with the small random write speeds.

by **xkxx** » Wed Mar 14, 2012 2:33 am

@rmm200: that card is really awesome. Where did you get it?

by **rmm200** » Wed Mar 14, 2012 2:36 am

Patriot 32GB Micro SDHC in adapter, hanging off a hub:

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read :    18.298 MB/s
Sequential Write :     5.220 MB/s
Random Read 512KB :    16.713 MB/s
Random Write 512KB :     0.799 MB/s
Random Read 4KB (QD=1) :     2.032 MB/s [   496.0 IOPS]
Random Write 4KB (QD=1) :     0.007 MB/s [     1.6 IOPS]
Random Read 4KB (QD=32) :     2.137 MB/s [   521.8 IOPS]
Random Write 4KB (QD=32) :     0.015 MB/s [     3.8 IOPS]

Test : 50 MB [H: 0.0% (0.0/29.9 GB)] (x5)
Date : 2012/03/13 19:33:20
OS : Windows Vista Ultimate Edition SP2 [6.0 Build 6002] (x64)

Abysmal write speed - I will do some more testing on this card.

For now - not suitable for Pi...

by **rmm200** » Wed Mar 14, 2012 2:38 am

My SanDisk Ultra is from Costco (US, $17.50). Looks ideal for Pi.

by **rmm200** » Wed Mar 14, 2012 5:06 am

Patriot 32GB Class 4 Micro SDHC in adapter, hanging off a hub:

Did a full test of this device; no errors found on read or write.

Ran the performance test again - about the same as first run.

Seems a suitable device for storage of videos and movies - but not for anything requiring random i/o.

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read :    17.922 MB/s
Sequential Write :     5.218 MB/s
Random Read 512KB :    16.995 MB/s
Random Write 512KB :     0.798 MB/s
Random Read 4KB (QD=1) :     2.041 MB/s [   498.2 IOPS]
Random Write 4KB (QD=1) :     0.007 MB/s [     1.6 IOPS]
Random Read 4KB (QD=32) :     2.136 MB/s [   521.4 IOPS]
Random Write 4KB (QD=32) :     0.016 MB/s [     3.9 IOPS]

Test : 50 MB [H: 0.0% (0.0/29.9 GB)] (x5)
Date : 2012/03/13 22:05:24
OS : Windows Vista Ultimate Edition SP2 [6.0 Build 6002] (x64)

by **semtex** » Wed Mar 14, 2012 5:31 am

So there's a potential problem with microSD cards. According to the Fedora remix site (http://zenit.senecac.on.ca/wik.....stallation) they say, "You need an SD or SDHC card, with a capacity of 2GB or more. (Good-quality class 4 cards usually work well). Do not use a MicroSD card with an adapter -- it will not be recognized by the Raspberry Pi."

by **Chromatix** » Wed Mar 14, 2012 7:09 am

semtex said:

So there's a potential problem with microSD cards. According to the Fedora remix site (http://zenit.senecac.on.ca/wik.....stallation) they say, "You need an SD or SDHC card, with a capacity of 2GB or more. (Good-quality class 4 cards usually work well). Do not use a MicroSD card with an adapter -- it will not be recognized by the Raspberry Pi."

No, that's BS. The Foundation have tested MicroSD cards with adapters and found them to work.

Cards supporting the UHS signalling modes (which appears to include most Class 10 cards, regardless of size) are currently problematic, but a fix is probably going to appear sometime.

by **AlexPT** » Wed Mar 14, 2012 9:37 am

Good post! Hope more people make this. And use the same test settings than semtex.

But we need more information from the SD cards, the "ref model" number.

Because, even if the name its the same, some time cards got diffident ref model.

Keep this going, and keep this clean from chat talk.

by **GrahamC** » Wed Mar 14, 2012 1:40 pm

Is there any way to find the manufacturer's part number of a SD card ?

If I do lsusb -v on a x86 linux system it just tells me the product details of the SD/USB adapter, with no information on the SD card plugged into it.

Hopefully when people start receiving their Pi they will post here what card(s) they have tried and how well (or not) those card(s) worked.

by **abishur** » Wed Mar 14, 2012 1:59 pm

Chromatix said:

semtex said:

So there's a potential problem with microSD cards. According to the Fedora remix site (http://zenit.senecac.on.ca/wik.....stallation) they say, "You need an SD or SDHC card, with a capacity of 2GB or more. (Good-quality class 4 cards usually work well). Do not use a MicroSD card with an adapter -- it will not be recognized by the Raspberry Pi."

No, that's BS. The Foundation have tested MicroSD cards with adapters and found them to work.

This is not BS, this is in reference to the Fedora Remix disto only. It is a confirmed and accurate report from the Fedora Remix peps themselves. As far as I am aware there has not been an issue with the microSD cards in adapters on the other various distros, but it is an accurate and true statement for the Fedora Remix for the moment.

by **rmm200** » Wed Mar 14, 2012 3:16 pm

The statement from the SD Standards organization is:

"Only the form factor, size, and number of pins and “with or without” of the write protect switch of the miniSD memory cards/microSD memory cards are different from the standard SD memory card. The logic and electronics of both the miniSD memory card/microSD memory card and the SD memory card are identical. "

https://www.sdcard.org/consumers/faq/#sdvsmini

With identical logic and electronics, I am curious to see how the Fedora remix is able to fail on one and not the other. It is obviously not a boot loader issue. I more suspect they tested a Class 10 card...

I will certainly be going with Micro SD in any case - it is a much more useful form factor.

by **liam.lah** » Wed Mar 14, 2012 8:05 pm


I point you to this thread. http://forum.xda-developers.com/showthread.php?t=1005633

We had this same discussion in the Nook Color community (you can boot an OS from SD card on the nook)

Benchmarks were done, and issues were reported with the higher class ones (boot loops, freezes etc.)

We pretty much came to a consensus that the Sandisk Class 2 or 4 in 8gb or 16gb had orders of magnitude

better results. Assuming that the full size sd cards have similiar benchmarks. If i had to take a gamble on an SD card

It would be a class 4 sandisk.

by **rmm200** » Wed Mar 14, 2012 8:19 pm

The issue at hand is not what class SD card to use - it is what form factor.

The Foundation says MicroSD will not work. Some of us are waiting to try it ourselves.

by **alexeames** » Wed Mar 14, 2012 8:41 pm

Isn't comparing lots of different cards with different setups of questionable worth?

Some people might have faster card readers etc. Just sayin'

For a proper test, they should all be done on the same rig.

by **rmm200** » Wed Mar 14, 2012 8:56 pm

If your serial read times to random read times is on the order of 100 to one - that is not affected by the reader you use.

by **jojopi** » Wed Mar 14, 2012 9:06 pm

rmm200 said:

The Foundation says MicroSD will not work. Some of us are waiting to try it ourselves.

The foundation has said that MicroSD adapters do work, subject to the usual caveats about individual card compatibility:

http://twitter.com/Raspberry_P.....9043450880

That is what you would expect, given that the different sizes are electrically indistinguishable.

Seneca's claim that MicroSD "will not be recognized" cannot logically be supported without them having tried every card in existence. It is at the very least an exaggeration and should not be taken at face value.

In the extremely unlikely event that card compatibility varies between distros, this could be addressed by swapping kernels.

by **semtex** » Wed Mar 14, 2012 9:21 pm

@alexeames: You are quite correct. If this was a proper scientific test and we were looking for absolutes then yes everything should be constant and the SD card should be the only variable. But as @rmm200 has pointed out, we are looking at orders of magnitude of differences.

Additionally USB 2.0 has a maximum data rate of 60Mb/s which easily exceeds the data rate of the fastest SD cards so for this particular test, equipment variability such as internal/external reader/USB2.0/USB3.0 has little significant impact on the results.

My objective with starting this post was to excite the mass of the community to take 10 minutes to capture the performance of their SD card. The vast majority of SD cards will be perfectly fine for RasPi but I hoped to identify those cards which should be avoided and maybe find a few that are particularly suited for RasPi.

I know I coloured my own post by commenting on possible issues with MicroSD cards. That was my bad. Maybe future comments can use a separate thread and we keep this thread just to capture results.

Thanks

by **liam.lah** » Wed Mar 14, 2012 9:55 pm

rmm200 said:

The issue at hand is not what class SD card to use - it is what form factor.

The Foundation says MicroSD will not work. Some of us are waiting to try it ourselves.

When there is such a vast differences between the performance of different classes and brands, why is that not an issue?

by **cehbab** » Thu Mar 15, 2012 12:28 am

AData 8GB SD Class 10:

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read :    15.537 MB/s
Sequential Write :    12.364 MB/s
Random Read 512KB :    15.358 MB/s
Random Write 512KB :     1.821 MB/s
Random Read 4KB (QD=1) :     6.223 MB/s [ 1519.2 IOPS]
Random Write 4KB (QD=1) :     0.016 MB/s [     3.9 IOPS]
Random Read 4KB (QD=32) :     6.005 MB/s [ 1466.0 IOPS]
Random Write 4KB (QD=32) :     0.017 MB/s [     4.2 IOPS]

Test : 50 MB [G: 0.0% (0.0/7879.0 MB)] (x5)
Date : 2012/03/15 11:15:42
OS : Windows XP Professional SP3 [5.1 Build 2600] (x86)

by **rmm200** » Thu Mar 15, 2012 2:37 am

liam.lah said:

When there is such a vast differences between the performance of different classes and brands, why is that not an issue?

I really think you will do better looking at specific test results here than at classes or brands. For the Pi, and the way the SD card will be used, a Class 6 or even a 4 will probably be better than a Class 10. I have a personal bias for SanDisk Ultra Class 6, but we may find a brand and class that does significantly better. Class 10s I have seen seem to have humungous write buffers, and those have to be flushed on small writes. Not good for random I/O....

by **alexeames** » Thu Mar 15, 2012 9:46 am

Ok. I'll play then. This is the data for a 2 Gig Cheapo blue Sandisk SD card I've had since 2006 (camera use)

Alex Eames RasPi.TV, RasP.iO

by **alexeames** » Thu Mar 15, 2012 9:49 am

Image didn't work. Here's the data

-----------------------------------------------------------------------
CrystalDiskMark 3.0.1 x64 (C) 2007-2010 hiyohiyo
Crystal Dew World : http://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 byte/s [SATA/300 = 300,000,000 byte/s]

Sequential Read :    10.265 MB/s
Sequential Write :     5.775 MB/s
Random Read 512KB :    10.177 MB/s
Random Write 512KB :     2.159 MB/s
Random Read 4KB (QD=1) :     2.532 MB/s [   618.1 IOPS]
Random Write 4KB (QD=1) :     0.027 MB/s [     6.7 IOPS]
Random Read 4KB (QD=32) :     2.741 MB/s [   669.1 IOPS]
Random Write 4KB (QD=32) :     0.036 MB/s [     8.7 IOPS]

Test : 50 MB [E: 17.2% (333.0/1938.1 MB)] (x5)
Date : 2012/03/15 9:46:54
OS : Windows 7 SP1 [6.1 Build 7601] (x64)
SANDISK 2Gb SD cheapo (blue)

by **Kernel** » Thu Mar 15, 2012 10:17 pm

https://www.amazon.co.uk/gp/product/B000OF2F36

Kingston - Flash memory card - 8 GB - Class 4 - SDHC

Windows 7 Home Premium SP1 64Bit using DiskMarkX64.exe and internal card reader:

SD Card Benchmarks

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