Recommended SD Card Size


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by ElectroPulse » Sat Jan 28, 2012 11:57 pm
Hello, all!

I aplogize if this is a dumb question, or if the answer is easily found…

Anyway, what is the minimum recommended SD card size for use in the RPi? I am not sure how large the OS would be in this type of device, since all I've ever dealt with have been standard computers. I am aware that there are some very small OSs (like 12mb I've heard), but I am not sure what the size of the RPi's OS will be.

Also, I have seen threads where people have mentioned something like "This card is supposed to work with the RPi..." So... does that mean some won't? What is required for a card to work with it?

Also, any recommendations for low-priced decent-quality SD cards are welcome (though that is not the purpose of this thread).

Thanks!
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by Chromatix » Sun Jan 29, 2012 12:20 am
The size of card required will certainly depend on which version of Linux (or some alternative like RiscOS) you plan to use with it.  In most cases a 4GB card will work, though if you plan to use a full-size distro (eg. Gentoo, Fedora) I would strongly suggest getting a larger size so that there is room for nontrivial files too.  A lightweight distro (eg. Arch) however might still be comfortable on a 2GB card.

Cheap SD cards can be a false economy, especially as a poorly designed one might wear out quickly when subjected to a Linux filesystem.  OTOH I have found that quality is not really correlated with price either - sometimes a good card turns out to have a low price tag for some reason, and some of the most expensive cards I've tried turned out to be total lemons.  See my most recent post in the Class 10 thread for some interesting details.

The tl;dr version is that SanDisk are almost certainly the best brand to get at the moment - they have three main SD-card product lines which are all decent.  If SanDisk is not available, then either Transcend or Verbatim are tolerable substitutes - but avoid the Class 6 Transcend cards in capacities over 4GB.  Kingston are to be avoided like the plague.

HTH.
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by WereCatf » Sun Jan 29, 2012 11:19 am
I atleast will be going with a 16 gigabyte class 10 one, they've got the best gigabyte per euro ratio over here and class 10 ones can be found plenty.

My setup is perhaps a bit different than most here, though, as I have a Linux-server already running 24/7 and so I am planning to run Linux on RPi over NFS and only use the SD for swap -- SD cards have great seek times, so they excel at such workloads -- and small cache files.

As to what brands I deem reliable: I cannot really say much more than that I too echo the sentiment that Kingston seems very unreliable. I've got several A-Data ones and they've worked just fine, Kingstones ones haven't.
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by rurwin » Sun Jan 29, 2012 11:56 am
16GB only used for swap? If it used all that it would be at a standstill. Save your money and get a load of 2GB cards or even 256MB, second-hand if possible.

From my experience with the eeePC, I"d say your SD card will only be used for the OS and applications. Any files of any value, or size, will be on a USB stick. At least that"s the way I found myself working.

So 16GB would probably be wasted even if you don"t use it only for swap. For a first purchase something that fits the OS with a bit of headroom would be my choice. Once I had a particular project in mind — that maybe required a large application to be installed or big files like a media player — then I may splash out on a larger SD. But even then, segregating your data from your OS may be a good idea in case one or the other breaks down.

That"s if it isn"t your main PC. If it is, then things may be different.
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by WereCatf » Sun Jan 29, 2012 12:02 pm
rurwin said:


16GB only used for swap?


If you had read the sentence fully you would have noticed the "and small cache files" at the end of it.


If it used all that it would be at a standstill.


Linux doesn't slow down even if you have ridiculously large swap, it only uses what it needs and as such you could have a 16GB swap partition just fine. It wouldn't make any sense, but it would still work just as it should.


Save your money and get a load of 2GB cards or even 256MB, second-hand if possible.


NEVER buy Flash - media second-hand, you have absolutely no way of gauging how used the cells are.


From my experience with the eeePC, I"d say your SD card will only be used for the OS and applications. Any files of any value, or size, will be on a USB stick. At least that"s the way I found myself working.


As I said, I will be running the OS itself from NFS. No need for USB sticks.


So 16GB would probably be wasted even if you don"t use it only for swap.


I much rather buy something reasonably-sized that can later on be used for something else, too. If I went with a 2GB one it would be absolutely useless for anything reasonable other than booting off of. Besides, a 16GB class 10 costs 7 euros, a 2GB one costs 5 euros, why would I choose the smaller one?
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by rurwin » Sun Jan 29, 2012 12:17 pm
WereCatf said:


rurwin said:


If it used all that it would be at a standstill.


Linux doesn't slow down even if you have ridiculously large swap, it only uses what it needs and as such you could have a 16GB swap partition just fine. It wouldn't make any sense, but it would still work just as it should.


True. However my point was that if Linux was using 16GB swap, then it would have so many programs loaded, most of them with no pages actually in RAM, that it would spend all its time paging stuff in and out of swap and no time running code. Like you say, it wouldn't make sense.


NEVER buy Flash – media second-hand, you have absolutely no way of gauging how used the cells are.


In general, excellent advice. However in this case, when it's just for swap (and maybe for those cached files), what will you lose? I doubt you would get any corruption, the space would just slowly reduce. You might start to see bad sectors, but Linux will cope with that.

The rest of my post was aimed at the OP, not your situation.

I would agree that if the difference between 2GB and 16GB is €2, then go for it. (Although a cash-strapped teenager may disagree.) That's not the price differential I see here.
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by Themanhunt » Sun Jan 29, 2012 12:41 pm
I believe that most Linux operating systems want at least 10gb, so I would recommend a 16gb one.
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by Benedict White » Sun Jan 29, 2012 12:46 pm
Themanhunt said:


I believe that most Linux operating systems want at least 10gb, so I would recommend a 16gb one.


Really? Standard Arch is 7.5GB but you only need a minimum of say 150MB. (Can't do huge amounts with it, but can run up various servers.)
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by WereCatf » Sun Jan 29, 2012 1:21 pm

In general, excellent advice. However in this case, when it"s just for swap (and maybe for those cached files), what will you lose? I doubt you would get any corruption, the space would just slowly reduce. You might start to see bad sectors, but Linux will cope with that.


Uhh. Swap getting corrupted IS bad. In the least it will crash the application, more likely it will crash the whole system and possibly result in corrupt filesystems.
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by Prometheus » Sun Jan 29, 2012 3:03 pm
Since the size thing seems to be being adequately covered by other posts, I just wanted to pop in to warn against buying flash-media on eBay - it's a VERY bad idea. :P
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by WereCatf » Sun Jan 29, 2012 4:15 pm
Prometheus said:


Since the size thing seems to be being adequately covered by other posts, I just wanted to pop in to warn against buying flash-media on eBay - it's a VERY bad idea. :P



I agree with Prometheus here: it's quite common for people to sell Chinese-imported cards where the cards aren't exactly what they claim to be. There's this Finnish eBay-like site called huuto.net where I bought one no-brand card just to prove that they're fake and I was indeed correct; the seller advertised them as 32GB class 10 cards and they indeed did report themselves as such when plugged into my PC and my phone, I could copy full 32 gigabytes of stuff into them, but only the first 1 gigabyte of the stuff was actually readable. Then I checked the speed next and indeed, the cards were at best class 4, not even close to class 10. Turns out the seller on huuto.net didn't know that they were fakes, he had been duped into selling them by some Chinese person who ships those things to Finland.

Some signs to look for: if the card is seriously underpriced compared to competition, it likely is a fake. Similarly, if there is no manufacturer information, phone numbers or address on the packaging it most definitely is a fake.
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by Lynbarn » Sun Jan 29, 2012 4:22 pm
I have just got some SD cards to go in my 'Pi starter set – SanDisc 4GB Secure Digital cards – I got 4 for under £4 each, from Amazon UK, including free postage! they should allow me to get things moving. If they are not as described :( (the vendor seems well regarded) I can always get my money back from Amazon, If I need higher capacity, i can get some more later :)
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by itimpi » Sun Jan 29, 2012 5:37 pm
I thought I remembered seeing posts at one time that suggested the RPi might have trouble with Class 10 SD cards! Does anyone have definitive update on this?
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by patmage » Sun Jan 29, 2012 6:09 pm
Not so much related to size, but when looking for benchmarks on SD cards should I be more focused on things like 4KB Random Read/Write performance or Average I/O operations/second or something else like access times?

I've seen benchmarks of the SanDisk Extreme having almost 10 times the I/O operations than other SD cards, but only average random Read/Write, and wondering if it was worth the closer to $2/GB compared to others half that price.
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by Chromatix » Sun Jan 29, 2012 6:46 pm
Based on my benchmarks, the SanDisk Extreme is as much as 2-3 times as fast as bog-standard Class 10 or Class 6 cards, when used with a good Linux filesystem like ext4.  The synthetic measurements of random access or sequential performance don't really capture filesystem performance accurately, although there is a fairly good (but not infallible) correlation between random write performance and filesystem write performance.

The SanDisk Ultra and blue Class 4 cards are also rather good, provided you get one that was made sometime in the past few months – ie. buy one now rather than digging through your spares.  They might be available for much less money than the Extremes, especially in higher capacities, but offer nearly as good performance in practice.

There doesn't seem to be any particular problem with Class 10 cards in general, but some specific manufacturers tend to use very low-quality components in the name of minimising costs.  The principal offender here is Kingston, but I suspect that some other brands are rebadges of Kingston cards.

Out of the 15 name-brand cards I have tested (in a TrimSlice, which is as close to a real R-Pi as I can get so far), about half of which are Class 10, only a Kingston card failed to complete a simple "format, untar, copy" benchmark run.  All fifteen cards (including the Kingston) have repeatedly completed a synthetic benchmark.

Transcend, SanDisk and Verbatim are all known-good brands in my book, but SanDisk is clearly the performance leader.
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by ElectroPulse » Sun Jan 29, 2012 8:20 pm
Alright, thank you all for the replies!

Ok, it looks like I'm going to be aiming for Sandisk cards… I am thinking about picking up 1-2 16gb, and 2-4 4gb-8gb cards, depending on how the prices are.

Anyone have any recommendations of a reputable US-based retailer that sells SD cards for low prices? WereCatf mentioned 7 euro 16gb cards (about $9 usd), and am wondering if anyone knows of a reputable US retailer with comparable prices. I've been looking on Newegg (basically the only site I look at tech items on, other than ocassionally Tigerdirect), but they're prices are nowhere near that low. (I've also checked Amazon, but am not sure whether the cards I am looking at are legit… I've heard that 30% of the SD cards on the internet are fakes…For example, is this one fake? (I'm guessing so, based on the really low price) http://www.amazon.com/SanDisk-.....038;sr=1-1)

Thanks!
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by Chromatix » Sun Jan 29, 2012 8:57 pm
Well, that *could* be a genuine January sale, but notice that it's from an affiliate and not from Amazon themselves - that's a red flag, apparently.  Because fakes are so ludicrously common, only buy directly from a well-established vendor.

I would be very suspicious of prices much below $1 per GB, especially for a premium brand.
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by laszlo » Sun Jan 29, 2012 9:39 pm
Is there the possibility of using some type of fast SSD, through one of the other interfaces on the Pi maybe? I realize all these flash memory things are 'solid state' but I mean, whether it's artificially slowed down somehow or whatever else, the USB and SD/CF ones are really slow compared to the SATA or PCIe ones (even though there's a ton of inefficiency in the ones that pretend to be hard disks, in practice they're fast).  USB sticks get 5-10MB/sec writes whereas there are now SATA SSD packages that claim 500MB/sec read/write, and of course there are multi channel RAID type setups that work through the PCIe bus and do 2-3 times that.

Is the SD card expected to be 'better' for mass storage than the USB ports?  Would it be better to use one of these SanDisk Extreme SD cards that were mentioned, or maybe a more complicated contraption like USB port -> enclosure -> SATA SSD?  In practice what ends up being the bottleneck?
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by dukla2000 » Sun Jan 29, 2012 9:54 pm
laszlo said:


Is the SD card expected to be 'better' for mass storage than the USB ports?  Would it be better to use one of these SanDisk Extreme SD cards that were mentioned, or maybe a more complicated contraption like USB port -> enclosure -> SATA SSD?  In practice what ends up being the bottleneck?


Exactly the question I am asking myself and we plain won't know until we have production Pi in our hands. My reading of JamesH throughput on his alpha-Pi is that the SDcard port on the Pi is significantly slower than the USB port, but I note Chromatix opinion that could have been worst case stuff and a decent SDcard on a production board could be completely different.

My plan is to hold off any (more) purchasing until I have a board. Then check if my existing farm of SDcards make any noticeable difference in Pi performance. If not work on putting storage via the USB (or LAN), else put a nice (probably Sandisk based again on all Chromatix work & posts) SDcard in the Pi.
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by WASD » Sun Jan 29, 2012 10:06 pm
I'm going for 8GB. It should be enough for OS and some extra storage. I have a usb harddrive too (with external power) and some flashdrives if i need more storage.
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by Jessie » Sun Jan 29, 2012 11:19 pm
Chromatix said:


The tl;dr version is that SanDisk are almost certainly the best brand to get at the moment - they have three main SD-card product lines which are all decent.  If SanDisk is not available, then either Transcend or Verbatim are tolerable substitutes - but avoid the Class 6 Transcend cards in capacities over 4GB.  Kingston are to be avoided like the plague.

HTH.


Sorry but I don't agree with you here.  My wife is a photogapher and SanDisk is typically the most likely not to work in any given camera.  She has several SLRs from Nikon, and Olympus, and a couple Sony point and shoots and several of them needed firmware patches to work with SanDisk cards and the newer Nikons still don't work with class 10 SanDisk cards.  I have some PNY and other generic brands that work ok but are slow.  But dispite your hatred for them Kingston class 6 cards are the fastest, lowest latency, and most dependable out of all the cards I own (0 filures yet,) and they get filled erased and dumped to NAS at least once a month.

The point I'm going to make here is that most of these cards arn't even made by the people who's sticker is on the label.  You can buy one SanDisk and have amazing results and I can buy one and have poor results (Just like I can have great luck with Kingston and you can't.)  The same goes for any brand, and then there are some chipsets, and readers that have various issues with each card.  We arn't really going to know what is best for these boards until the hardware becomes avalible.
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by Jessie » Sun Jan 29, 2012 11:24 pm
laszlo said:


Is there the possibility of using some type of fast SSD, through one of the other interfaces on the Pi maybe?

enclosure -> SATA SSD?  In practice what ends up being the bottleneck?


The fastest interface is the USB 2.0 interface.  You would be wasting your money (unless you really really needed awsome random read speeds.)   The teroetical max of USB 2.0 is 60 MB/sec now realize that there is packet overhead and USB 2.0 is not full duplex, plus on the R-Pi it shares bandwidth with everything.  So a SSD would saturate a USB 2.0 bus easily, as would a USB HDD.  The only benefit to the SSD is random seek times,  Your call but I think it is money down the toilet.
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by Chromatix » Mon Jan 30, 2012 12:24 am
Jessie said:


Sorry but I don't agree with you here.  My wife is a photogapher and SanDisk is typically the most likely not to work in any given camera.


I just stuck the SanDisk Extreme into my Panasonic Lumix compact - the only camera I have which will accept a full-size SD card.  The camera had no trouble formatting and then taking photos and video onto it.  Then again, the shop sold me a SanDisk Ultra to go with it in the first place - that's where I got the older version of that range from.

My Canon video camera also works just fine with a 256MB SanDisk MiniSD card (which is used for still photos only - video goes onto tape).

I respectfully suggest that the SanDisk cards your wife has used before might not have been genuine - or else DSLR firmware is a lot more ropey than their prices allow any reasonable person to expect.  I could however ask a couple of photography buffs at the office what they use.

I also have an old Nikon, but it takes CF cards which are not relevant here.

In one respect I do agree: it will be a lot easer to confirm one way or another once we have the real thing to hand.  So far I have only been able to investigate using a couple of USB card readers and my TrimSlice.
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by Chromatix » Mon Jan 30, 2012 12:29 am
A USB-attached hard disk will be the most reliable way of getting large amounts of fast storage attached.  It doesn't have to be SSD, but note that mechanical drives are more sensitive to being knocked or dropped.

USB Flash drives are actually even worse than SD cards for performance and wear.  They're built on the same principles, but without the performance standards to keep the cost cutting reined in.
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by Vindicator » Mon Jan 30, 2012 3:11 am
I have used Sandisk SD cards for many years with little to no problems, I still have a 128 mb and 256 mb that i still use .

As for size I am currently using a celeron 900 on a old mb with 320 mb ram to make this post and it has puppy linux 5.2.5 on it and currently has a 2.1Gb hdd installed and there is 1.5 of 1.9 free on the drive.

On my main PC I have virtual box with Debian squeeze and LXDE desktop straight from the video guides from Liam Fraser and with python and such loaded it is using 1.5 Gb of 8Gb set up for it, and thast is with 5 snapshots.(mind that there is a lot of wasted bytes in that this is on a 1.5 Tb hdd and the cluster size is very large)

I think that 4 Gb will be sufficient to fire up the device and program with it, that said I think the next option would be a mini external drive used with a powered hub to be the best way to extend your storage capacity as for dollar on dollar comparison.

SSD are fast but look at the capabilities of the main hardware the Raspi and after sharing the bus with all devices connected through the 9512 chip what advantage would a SSD serve except for maybe a wow factor.

Throw in the interrupts of that for polling amongst the devices and speed is of little to no matter.

Let the beatings begin

I suggest keep it simple or buy a much faster device.( there are people out there with more money than sense just to let you know)
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