kanniya
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Query on micro SD card support in B+?

Thu Aug 07, 2014 10:58 pm

Hi all,

Just wanted to check if the B+ unit supports micro SD card ? Samsung Electronics 32GB EVO Micro SDHC Upto 48MB/s Class 10 Memory Card

- Kanniya

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Speedwell68
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Re: Query on micro SD card support in B+?

Thu Aug 07, 2014 11:10 pm

I don't see why it wouldn't work.

jbowler
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 12:41 am

kanniya wrote:Just wanted to check if the B+ unit supports micro SD card ? Samsung Electronics 32GB EVO Micro SDHC Upto 48MB/s Class 10 Memory Card- Kanniya
It'll work with that or any other 32GByte card. The lower the class the lower the speed. That's actually a UHS1 card so it will probably be a lot faster than the 32GByte Sandisk (non-UHS1) card I have in my B+.

There are, however, a lot of caveats. These aren't RPi specific or, indeed, specific to the Samsung card.

1) Based on reading reviews on the US Amazon an increasing number of sellers are selling 32GByte and (particularly) 64GByte flash cards that are actually 4 or 8 Gbyte cards that have been reprogrammed to believe they are 8x bigger. The computer *inside* the card doesn't realize this until the user has actually written a full 4/8Gbyte of data to the card, at which point the card fails. Google "fake SD card". Well known brand names have the problem, it's the highwayman dilemma; if you are going to be hung for robbery at gunpoint you may as well take the chance of not being hung for murder. Well, it's also the Dude problem; Dudes ("Doods") have really big cards but nothing on them, so they never notice.

2) The hardware supports that card, but the operating system has to as well. How well the card works depends on how well the operating system supports it.

3) Linux doesn't support SD cards used as operating system file systems very well. There is support in current RPi Linux versions for Samsung's F2FS file system, it seems reasonable that the Samsung card will probably work very well with F2FS as a root partition (you can't change the boot partition, it has to be FAT32, but it's not written very much so it doesn't matter.) I run F2FS on my B+, it's ok.

4) Even with F2FS how long the card lasts will still be a function of how carefully you configure the operating system. Actually writing temporary data to the flash card is probably a mistake, unless you have to because you hit the limit of the B+ DRAM. Whether this matters depends on how much temporary data your application generates; I can't imagine it being a problem with a controller application but if the application is doing a lot of video that might be different.

John Bowler

kanniya
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 1:24 am

Thank you Speedwell68.

@ John,
First off ... Thank you for the detailed explanation.
I recently purchased a B+ (still in transit)
I am planning to use B+ as a media center of sorts.
I'll saw that Sling player now has XMBC support. http://wiki.xbmc.org/index.php?title=Slingbox
So yes I'll be using for video.
Do let me know if this will be a problem ?

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AndrewS
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 1:40 am

jbowler wrote:The lower the class the lower the speed.
As has been mentioned many times, that's true for large single reads and writes (e.g. that a digital camera might perform when taking megapixel photos), but for random reads and writes (e.g. that an Operating System running on a Raspberry Pi will be doing) lower class cards can often perform better than class 10 cards. That's why the SwagStore cards are class 6.
That's actually a UHS1 card so it will probably be a lot faster than the 32GByte Sandisk (non-UHS1) card I have in my B+.
The SD-card-slot in the Pi is fixed at running at 3.3V, and isn't able to drop down to the 1.8V that UHS1 needs to work. So the Pi is always in non-UHS mode.
3) Linux doesn't support SD cards used as operating system file systems very well. <snip>
4) Actually writing temporary data to the flash card is probably a mistake, unless you have to because you hit the limit of the B+ DRAM. <snip>
For typical day-to-day usage patterns, on modern SD cards (which use decent wear-levelling algorithms), I can't imagine either of those actually being a problem? :?

Liamthe1st
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 6:24 am

:D hi,
I have two Pi+ and bought a 16GB micro sd Card which apparently is loaded with Google code!
It was advertised as learn how to code!
No instruction or Paper work. From Cool components.com. My question is do I break the sealed packet and insert the card? And hope instructions jump out at me? I have googled, google code no result!
Anyone know anything?
Or will it turn out to be a 2gb dude for £11.99 plus £2.49 shipping.
Dit Dah Dit Dah Dit

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Richard-TX
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 6:31 am

Is there a fsck for F2FS that doesn't crash when it encounters a file system problem?
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fruit-uk
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 6:52 am

Liamthe1st wrote::D hi,
I have two Pi+ and bought a 16GB micro sd Card which apparently is loaded with Google code!
It was advertised as learn how to code!
No instruction or Paper work. From Cool components.com.
Have you read the link from the order page?

http://googlecreativelab.github.io/coder/

silar
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 8:32 pm

I tried with the 16gb Samsung EVO card thinking it would work good.. but it was a no-go. Seemed to work kinda flaky. I was getting read and write errors on it.. Could have been that card I bought, but I definitely won't buy another Samsung EVO Micro SD card for any PI I have..

MrEngman
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Re: Query on micro SD card support in B+?

Fri Aug 08, 2014 9:06 pm

I've tried a couple of SanDisk 32GB microSDHC Ultra, UHS1 I think. Good speed.

And a great price, at my local Costco only £14.39.



MrEngman
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kanniya
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Re: Query on micro SD card support in B+?

Mon Aug 11, 2014 5:48 pm

@ all , Based off the response's i have got the Sandisk ultra. Thank you all for the valuable inputs, i really appreciate sharing your comments .

jbowler
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Re: Query on micro SD card support in B+?

Tue Aug 12, 2014 1:55 am

Richard-TX wrote:Is there a fsck for F2FS that doesn't crash when it encounters a file system problem?
Mine hasn't crashed yet. I guess it depends on what the problem is and what the bugs are in f2fs. I'm using Gentoo.

John Bowler

jbowler
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Re: Query on micro SD card support in B+?

Tue Aug 12, 2014 5:56 am

AndrewS wrote:
jbowler wrote:The lower the class the lower the speed.
As has been mentioned many times, that's true for large single reads and writes (e.g. that a digital camera might perform when taking megapixel photos), but for random reads and writes (e.g. that an Operating System running on a Raspberry Pi will be doing) lower class cards can often perform better than class 10 cards. That's why the SwagStore cards are class 6.
That doesn't help much unless someone has a list of card performance and even then I suspect it will depend almost entirely on the file system you put on the card. Anyway, it's moot; getting a class 6 card these days is almost impossible and getting a 32GB card that isn't class 10 may actually be impossible. (And the list I quote below is, I believe, seriously out of date and requires an enormous amount of work to produce...)
AndrewS wrote:
That's actually a UHS1 card so it will probably be a lot faster than the 32GByte Sandisk (non-UHS1) card I have in my B+.
The SD-card-slot in the Pi is fixed at running at 3.3V, and isn't able to drop down to the 1.8V that UHS1 needs to work. So the Pi is always in non-UHS mode.
I wasn't aware of that. It seems somewhat unfortunate, but I guess the chips that support UHS-I are currently quite a lot more expensive.
AndrewS wrote:
3) Linux doesn't support SD cards used as operating system file systems very well. <snip>
4) Actually writing temporary data to the flash card is probably a mistake, unless you have to because you hit the limit of the B+ DRAM. <snip>
For typical day-to-day usage patterns, on modern SD cards (which use decent wear-levelling algorithms), I can't imagine either of those actually being a problem? :?
Lots of small writes getting expanded to between 32 and 256kbyte each... See the extensive discussion here:

http://lwn.net/Articles/428584/

And the corresponding linaro page which has the detailed (though, I think, somewhat dated) numbers:

https://wiki.linaro.org/WorkingGroups/K ... CardSurvey

You can see from the table that the class of the card won't matter if you end up writing in units smaller than the minimum write size. In essence if you write a 4kbyte file to /tmp (quite likely) it might only get expanded to 8kbyte or it might mushroom to 256kbyte.

This is why I suggest that using F2FS with a Samsung card makes sense; the card is proprietary, but the F2FS operating system is open source and so can be used under Linux. If, on the other hand, you buy any other manufacturer's card there's no particularly guarantee that it will work because the other manufacturers don't provide file systems and, so far as I am aware, it isn't possible to run a standard Linux off a fat32 root.

John Bowler

GoodiesHQ
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Re: Query on micro SD card support in B+?

Fri Mar 13, 2015 8:34 pm

Just purchased this card:
http://www.ebay.com/itm/291400258636

128 GB certified Samsung Evo UHS-I for $28.66.

I hope the Evo's work because I've purchased too many already and this is a decent chunk of cash to spend on an SD card, even though it is a hell of a lot of storage for the money.

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LitterBugs
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Re: Query on micro SD card support in B+?

Fri Mar 13, 2015 10:24 pm

Did you read the comments for that seller before you bought? I would run the opposite direction from a seller with that rating....

Hope you get what you think you ordered.

LitterBug

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DougieLawson
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Re: Query on micro SD card support in B+?

Fri Mar 13, 2015 11:42 pm

That card is at least $12 too cheap, therefore it's very likely going to be a fake.
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pluggy
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Re: Query on micro SD card support in B+?

Sat Mar 14, 2015 9:55 am

GoodiesHQ wrote:Just purchased this card:
http://www.ebay.com/itm/291400258636

128 GB certified Samsung Evo UHS-I for $28.66.

I hope the Evo's work because I've purchased too many already and this is a decent chunk of cash to spend on an SD card, even though it is a hell of a lot of storage for the money.
A textbook example of how NOT to buy an SD card.
You deserve everything you get.

You need to be very careful with cards above 8GB (Genuine 8 GB are so cheap, its hardly worth faking them). Its not worth bothering with anything above class 4 or 6, becuase the Class is all about sustained write speed, which is entirely irrelevent when you're running an operating system.
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

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