Class 10 SD cards on the production boards

[MorgUK]

Hi, when are we going to know if faster/class 10 cards will work and if the issue is firmware or not etc?

Thanks.

[Chromatix]

I expect that's one of the things that will be looked at during the production testing now in progress.  If they still have trouble with some cards during that, I've given them some ideas on firmware modifications that might be viable workarounds.

As always though, we'll hear about it when it's properly established, and not before then.

[grumpyoldgit]

It astonishes me that so much time and effort is going into posts on the SD cards. It really isn't rocket science (or brain surgery, if you follow Mitchell and Web). Just buy a cheap SD card from a reputable manufacturer like Sandisk. Play.com and Amazon.com will sell you an 8GB Class 4 for just over a fiver, post free. Then, within 24 hours or so of launch, all the reports will come in with real life experience of what particular cards will or will not do. You can then go out and buy a Zoink 64GB, Class 12 Ultrabastard, safe in the knowledge that it is fast and reliable as you have read reports from other posters. Until then, all the discussion is largely speculation and you can concentrate on the important tasks of not reading the FAQ or wiki and sending posts asking when the board is available, that you don't agree with the distro chosen because it is crap, and can you run Skyrim on it?

[MarshallBanana]

Grumpyoldgit said:


You can then go out and buy a Zoink 64GB, Class 12 Ultrabastard, safe in the knowledge that it is fast and reliable as you have read reports from other posters. Until then, all the discussion is largely speculation and you can concentrate on the important tasks of not reading the FAQ or wiki and sending posts asking when the board is available, that you don't agree with the distro chosen because it is crap, and can you run Skyrim on it?



*lol*ed at that, thank you. i know have half-chewed liquorice all over my keyboard... good thing i have a black keyboard

[jamesh]

Black sticky keyboard.

[ElectroPulse]

Gives new meaning to "Sticky Keys"

[Chromatix]

In Finland it would not only be black and sticky, but salty as well.  (Salmiakki.)

[Chromatix]

Some good news for people interested in discounted SD cards from Amazon: as long as you buy directly from Amazon (ie. not from affiliates), you should be fine.

That is to say, I actually went and bought a couple of SanDisk 16GB cards - a blue Class 4 for under £10 and an Extreme for under £20.  The free shipping made them take almost a week to get here, but after testing they not only hold full capacity but appear to be genuine SanDisk based on their performance characteristics.

The blue card is not actually all that fast - it clearly uses the new, ultra-cheap-per-gigabyte TLC Flash for the bulk storage, and this means you really do get Class 4 performance and not much more for big files.  However, the SLC buffer in front of it helps a great deal with practical performance and should also make longevity a non-issue.  If you want 16GB for cheap, this is a good option.

For double the price, the Extreme offers more than double the performance across the board with the same capacity.  Note however that I have still not been able to confirm that the R-Pi can boot reliably from a UHS based card, because like everyone else, I don't have an R-Pi yet.

[Chromatix]

I made pretty graphs of my benchmark results.  Notice how the Class 10 cards are not so often faster than Class 4 or 6 equivalents in practice.

Synthetic benchmarks are on the left.  Practical ones, involving a real filesystem, are on the right.

[michel_noir]

Oh,

this is the best SD benchmark i ever saw

nice job

[AlexPT]

I really hope the Sandisk Extreme SDHC 30MB/s+ work

Or we gonna need to find some fast Class 4/6 ones

[Chromatix]

Given the current state of affairs, I think I should recommend the SanDisk Ultra series instead.  Those are Class 4, do *not* use the UHS bus, and unless I misread things, are already used widely by the Foundation.

They also happen to be the fastest Class 4 cards I've yet seen.

[AlexPT]

I hope the first people to get the rPi, test a lo of cards.

So we see the real performance under it, and compatibility.

And we get some table whit the data and card s/n.

[ferrymanr]

Slightly off topic but I wonder how fast R-Pi can handle a USB hard drive.  I was looking at booting from SD card and mounting the USB hard drive for all user data.

[Chromatix]

Probably about as fast as any USB 2.0 capable computer.  It depends a lot on the quality of the drive, and in the case of adapted hard disks, the quality of the adapter.

[jojopi]

Chromatix said:

But in order to support the higher speeds, the R-Pi must support 1.8V signalling.  This is a key difference not only between it and the TrimSlice, but also a probable key difference between the problematic Class 10 cards and the (working) slower ones.  These cards also support 3.3V for backwards compatibility - hence they still work in my TrimSlice - so switching to 1.8V is not necessary for booting, only for higher performance.
If this correlation can be confirmed, then a reasonably obvious fix in the GPU firmware should be sufficient - restricting it to 3.3V operation for all cards.  The operating system should then be able to switch to 1.8V if desired, since Linux is somewhat easier to debug than the firmware.


In the E14 webinar Q&A[1] at about 43:40, Eben appears to say that the Pi has a fixed 3.3V SD interface.  If that is the case then it is a mistake ever to attempt the SDR/DDR modes.  But the DS/HS modes should still work at 3.3V on all cards?

[1] youtube.com/watch?v=ALwTAH-3h84

[Chris.Rowland]

Chromatix said:


I made pretty graphs of my benchmark results.  Notice how the Class 10 cards are not so often faster than Class 4 or 6 equivalents in practice.

Synthetic benchmarks are on the left.  Practical ones, involving a real filesystem, are on the right.


That's a really nice set of benchmarks, its nice to see the SanDisk Extreme 4G I got from Amazon a few weeks ago at the top of the list

Thank you very much for all the hard work.

[Jim Manley]

ferrymanr said!:

Slightly off topic but I wonder how fast R-Pi can handle a USB hard drive.  I was looking at booting from SD card and mounting the USB hard drive for all user data.


In fact, the only directory that needs to remain on the SD card is the /boot directory. Everything else can be copied/moved to an external USB thumb, solid-state, or hard drive and the latter will likely provide the fastest resd/write speeds, have much greater capacity, and have a better performance/cost ratio. You will need an externally-powered USB hub to power a hard drive, however.

[dukla2000]

jojopi said:

In the E14 webinar Q&A at about 43:40, Eben appears to say that the Pi has a fixed 3.3V SD interface.  If that is the case then it is a mistake ever to attempt the SDR/DDR modes.  But the DS/HS modes should still work at 3.3V on all cards?
May well be true: the boot problem the puppy linux folk have ( http://www.raspberrypi.org/for.....emu#p62087 ) and their boot screen (http://i.imgur.com/TX3i6.jpg) indicate the Pi is indeed failing to switch to 1.8V


sdhci: Switching to 1.8V signalling voltage failed, retrying with S18R set to 0


It appears that then hangs. So in the short term if we hard code sdhci to not try any fancy modes could allow use of higher spec cards but in compatibility mode. And in the medium term maybe get 1.8V signalling (fixed?).

[rew]

I now understand that 1.8V signalling would require switching the VCCIO voltage on an IO bank of the Broadcom chip. This is not possible without hardware changes. Possibly it is terribly difficult (due to other things requiring 3.3V) to achieve at all.

[Chromatix]

With some help from dukla2000, I now have a real R-Pi to test with.

Results so far:

SanDisk Ultra 2GB: no problem (with Arch, after fixing config.txt for my monitor).

SanDisk (blue) 16GB: no problem (with Debian, no changes needed).

SanDisk Extreme 16GB: refuses to boot either the Arch or Debian images currently on the downloads page, or the Fedora Remix 14 image that I just downloaded. In each case it clearly loads the Linux kernel, then fails to detect the card within Linux. With Fedora, the "Failed to switch to 1.8V" message is clearly visible.

Time to go looking for (or to create) a patched kernel.

[Lob0426]

I used a PNY class 10 card on the Panda board. When I wrote an image to the card it was fast. But it took longer to setup Ubuntu than the class 4 SanDisk cards I tried first. When installing ubuntu updates it took twice as long as the class 4 cards. I now am using SanDisk Ultra class 6 cards they wrote the image twice as fast as the class 4 and half as fast as the class 10. Setup was faster than the class 4 and class 10. Updates installed faster than the PNY also.

Go with the class 6 cards, save money and get better overall performance. If you really need more speed/size transition to an USB HDD. The HDD is not twice as fast as the cards. It is the fastest of the options but also the most expensive. Mine cost me only a 12" USB SATA cord, I had the Seagate 120GB HDD lying around. I had the best overall performance with the USB HDD but you fill up a lot more desk space. The board plus a powered hub plus a USB HDD, then keyboard and mouse. Cords everywhere. The class 10 cards are not the fastest cards overall.

[Chromatix]

It would be more accurate to say that Class ratings are mostly *uncorrelated* to performance under Linux. As previously explained on this thread, the access patterns used to derive those speed ratings are much simpler than those required by typical Linux filesystems under load.

There are high-quality Class 10 cards that have very good performance (relatively speaking) under Linux, and Class 6 cards that have very poor performance - and vice versa. That's why I have repeatedly recommended SanDisk, as they currently make cards that are very tolerant of Linux' access patterns.

Right now I'm just trying to make my Pi boot with one of the Class 10 cards. This is harder than it should be, since the problem was supposedly solved a while ago but the easily accessible distro images still come with old kernels. Luckily I have a faster ARM based machine to build kernels with.

[Chromatix]

Okay, after installing the latest binary firmware, kernel and modules via another Linux machine, the SanDisk Extreme 16GB boots fine. I haven't tried more of my other cards yet, but I'm reasonably confident that the same fix will allow almost all of them to work.

This is good news, but raises the question of why outdated firmware is still up in the most obvious download locations. I think this needs to be rectified quickly.

[MarkUK2006]

I first purchsed a Class 6 Sandisk Ultra (with upto 30 MB/s speeds) but it didn't work. My next purchase was a Samsung Class 10 (with 24 MB/s read and 21 MB/s write), Model MB-SP8GA, its works a charm and boots really fast.