SD Card Recommendation

[njp]

Hello, so this is actually some info to add to the forum, with a question to boot.

I've been using a Lexar Premium Series 16GB SDHC that I had lying around from a digicam(http://www.amazon.co.uk/Lexar-Premium-C ... B008LBJZ56). No speed complaints really. Doing a rsync --progress of a 200MB file from my mount (Synology DS213+ via GbE) to the Pi (Onboard Ethernet) yielded an average speed of about 1.8MB/s, fluctuating between 2MB/s and 2.6MB/s often through the transfer. Wondering if the SD was a limiting factor, I then bought another one to try following research online.

http://www.amazon.co.uk/gp/product/B00J ... UTF8&psc=1

You wouldn't believe how much snappier the runeaudio UI is now, it's quite unbelievable. The spinning arrows in the middle of the screen that you see as you change pages, I barely see for a split second now. With the Lexar I saw it for at least a half second to a second between page changes.

So I then did the same transfer from my mount as above and got improved speeds - an average of 2.76MB/s but fluctuating between 3 and 3.5MB/s very often. The card is of course much faster having written the runeaudio image to it at 50MB/s roughly (the Lexar around 15 - 20MB/s), and the network throughput should theoretically be 10MB/s or thereabouts being 100mbit.

Which leads to a question - where is the bottleneck? Is it just the Pi's poor network performance? Can't actually seem to find detailed info online on the network throughput of the onboard ethernet unless it's just common knowledge now so it's unspoken about in forums.

Otherwise, I'd recommend the Samsung Pro SDHC if anyone doesn't want to run off USB or an SSD/hard drive.

[ACX]

Thank for your feedback about the SD card. We could add some useful informations about that kind of issues in the section of the documentation.
BTW, I also always experienced very low network transfer performances on the Rpi, with all kind of SD.

[njp]

Thanks for that - yep in that case I think I'm going to scrap trying to run the system off a Pendrive or SSD if there's never going to be a better throughput than what we see.

[Fishstix]

Hey Folks,

Out of curiosity I picked up the same Samsung Pro card you recommended, njp and you're dead right. Almost no latency, I now only briefly see a flash of the 'connecting' icon. I *was* running a Kingston 32 Gb Class 4. Kingston says that means "4MB/s minimum data transfer rate." Maybe higher read rate? The Samsung Pro, (Class 10) is supposed to have a 90Mb/s read speed, and it really shows.

The Kingston speed wasn't really an issue, it was reliable and quick enough. But this new SD card makes such a nice difference I think I would have a hard time going back. There's a SanDisk pro model out there too, with ~90Mb read speeds, it would be cool to hear if someone else finds similar results.

Debug Data comes back slightly faster, 3.2 seconds rather than 3.4, FWIW.

Thanks for looking into this, njp!

-Fishstix

[johnbanks]

@Fishstix and @njp

I’ve been interested in SD card & USB stick performance for several RPi projects and have tested a few. My results are in the attachment. The absolute values will not apply to RPi but the relative values may well apply. (UK cost is what I paid during the past 12/18 months and costs are coming down)

They have convinced me to put the second OS partition on a USB 3.0 stick and just boot from the SD card. And there are lots of people suggesting this on the Raspberry forums – not just for speed but to avoid card corruption, wear, etc. There are other postings on this forum too.

I picked up on the @Fishstix suggestion to run Debug with the thought of using the time taken as a benchmark. I tried it (Rpi B+ with iqAUDIO DAC+ running updated 0.3 alpha on an Integral Fusion 8GB USB 3.0 stick) – did it 4 times – 11.737, 3.887, 3.753 & 3.885 secs. I assume the first run involved a one-time set up?

So no evident benefit of using a USB 3.0 stick. But had a eureka moment and over-clocked my RPI B+ to TURBO mode via config.txt. Doing Debug 4 times gave 6.928, 2.359, 2.347 & 2.352 secs!

And the UI was much nippier – and on the basis of no evidence whatsoever, I imagined that things were ‘going better under the hood’ in general

[Fishstix]

Hey John,

That's some sweet info! Thanks for putting it together. I would not have expected a USB drive on a 2.0 port to run faster than a fast SD card; the manufacturer's specs usually read lower. Proof is in the pudding, though.

Reading more on the Pi forums, I am hearing that Class 10 SD cards are geared for generally higher sequential, single large file read/write rates. (e.g. 1080p recording.) Throw a few small files at them, and they struggle; they are not built for multitasking work, so maybe not the best medium for an OS to begin with. It makes me want to pick up a solid USB flash drive and see how it plays, even with the limited 2.0 ports. But then again, RuneAudio is, from what I understand, a pretty lean system anyways. Maybe it's multitasking needs don't much cramp an SD card's style? Either way, this new Class 10 makes a noticable difference; it's fast enough I can't count on my fingers anymore...

I usually get a high number the first round of debugging. In fact, the first time I debugged after re-flashing the drive, I got 1414198280.651 seconds. So *technically* the debug took 44.8 years. I'll post the results when they get done. After every re-boot I get a debug time that's notably higher than everything that comes after. Why? I have no idea. Subsequent runs seem to normalize. Of course, this is not a litmus benchmark test, but still useful, I think.

I would be interested in the overclocking, more because I like to fiddle than anything else. Seriously, this thing is already running like a top. I wonder how any of the DAC or DIGI hats would react to it? Somewhere on the forums there was something about running Quake 3 as a test to see how the RPi deals with heating as you incrementally speed it up. I have to assume that RuneAudio is going to have somewhat lower processing needs than a video game, and that pegging the highest recommended speed (I hear 1ghz...) would be just fine for it. More research is required, but let's be honest, this is probably going to happen. Looks like it's worked well for you!

Cheers!
-Fishstix

[johnbanks]

@Fishstix

If you’re minded to try overclocking then this is very informative ...



With over-clocking, my Debug time improved from 3.9 secs to 2.4 secs.

I just made the following changes to config.txt file ...

Add the line ...
force_turbo=1
... immediately after ##Turbo

Then uncomment the following 4 lines as below ...
arm_freq=1000
core_freq=500
sdram_freq=500
over_voltage=6

Has had no effect on my iqAUDIO DAC+

I guess tomorrow we get to be amazed/delighted yet again ... with the latest release

(Sorry if I’m teaching my grandmother )

[Fishstix]

[johnbanks]

@Fishstix

It's 1:13 hrs on 29 Oct now in UK - so 2:13 hrs in Italy.
No sign yet
I'm going to bed
Have fun