Sdhc - How Fast Is Fast Enough?

[yannv]

Here is a stand-alone on the Patriot 32GB Class 10.
http://www.ccereviews.com/reviews/patriot-memory-lx-series-32gb-sdhc-memory-card/

Thanks. That configuration didn't do well at all on small, randomly distributed writes. And the review says we can see it living up to Class 10 (which only covers sustained write speed) near a screenshot showing read speed. The IOMeter graphs above it say it does not, the Crystal disk mark says it does, so it probably requires a continuous stream of considerable length to do it.

Another stand alone (not so well done) for the Sandisk 32GB Extreme III Class 10
http://www.legitreviews.com/article/1172/1/

There is some data here. Not least of which is, for small writes the Lexar class 2 card outperforms the Sandisk 30MB/s ones. That's the controller and/or page size of a lower capacity card working.

Thanks for locating these. For now I think I'll be fairly happy with the card I got (Lexar class 6 8GB 133x pro) but I don't have a reader in which to test it (2 on order, unknown if they're good enough). Not to mention testing on the Pandora itself.

 

[Grench]

Not to mention testing on the Pandora itself.

And that is the crux of it. Until we have a few of these cards tested on an actual MP Pandora - everything else is speculation.

In the wintel world there are tons of packages to benchmark and test RAM, Disk, display, etc. Is there anything out there that can be compiled to ARM for us to use as a standard benchmarking suite for the Pandora?

After the Pandora gets released, I could see us having a thread with nothing but SD/SDHC benchmarking results - everyone reporting in what their card did. We had several of those on the Zodiac forums.

In the meantime there have been claims that the slower cards are as fast as anyone would/should need because of X where X varies between the bandwidth of a streaming movie to the bus capacity of the SDHC controller chip (24MB/sec) which may or may not be net over both, net for read/write or net unidirectional per card, or ?.

 

[yannv]

In the wintel world there are tons of packages to benchmark and test RAM, Disk, display, etc. Is there anything out there that can be compiled to ARM for us to use as a standard benchmarking suite for the Pandora?

There are several. The first that comes to bind is bonnie, but dbench and iozone (non-free but source available and has been built for arm) should also be capable. In a pinch, even dd can test sequential access, and it's not hard to write a testing program. The questions are 1) if they'll be easy to get at (i.e. in the pandora repository) and 2) easy to understand what the values mean to your workload.
Edit: both bonnie++ and dbench are in Ångström already.

 

[Chairman_Now]

yet some manufacturers used classes that weren't yet specified (class 10?)

PLEASE stop posting misinformation - you're the second person on this thread to crap it up with ignorance. There is a "real" Class 10. From the wikipedia page on sdhc:

On 21 May 2009, Panasonic announced new "class 10" SDHC cards, claiming that this new class is "part of SD Card Specification Ver.3.0".[9] Toshiba also announced cards based on the new 3.0 spec[10] As of December 2009[update], the SD Association's Web site does not include information on this new class or new specification.

Panasonic invented SD/SDHC, and they're the first to come out with Class 10. If they say that it is spec, it is.

To get back on target: I'd like a simple test where a known-fast SD card is speed tested on a PC with a fast SD interface, and then tested on the Pandora. Perhaps both under Linux.

That way, I can grab what I need when they go on sale. Prices on SDHC cards have generally gone up in the last year, at least for 16GB size. This would be very useful information.

 

[yannv]

PLEASE stop posting misinformation - you're the second person on this thread to crap it up with ignorance. There is a "real" Class 10. From the wikipedia page on sdhc:

On 21 May 2009, Panasonic announced new "class 10" SDHC cards, claiming that this new class is "part of SD Card Specification Ver.3.0".[9] Toshiba also announced cards based on the new 3.0 spec[10] As of December 2009[update], the SD Association's Web site does not include information on this new class or new specification.

Panasonic invented SD/SDHC, and they're the first to come out with Class 10. If they say that it is spec, it is.

Very well. Pardon me for being a part of the public to whom this marketing brand is targeted, who have no access to that specification. Looking at the public spec, on the other hand, maybe another metric to compare these cards by is Allocation Unit size. The precise requirements for the speed measurements are removed in the public spec, so most of the world cannot reliably confirm if a card matches its classification. AFAICT the speed guarantee is likely to be about writing entire unused AUs, which might mean AU and RU sizes are relevant metrics for cards, too. It's just getting more complex :/

Maybe it's time to find or make a utility to read the parameters the cards present.

 

[Viral18]

Now if the Pandora could run SDXC cards that would make my day (2tb storage on a portable device *drools*), until then 2 class 6, 16gb SDHC's will have to do

 

[WizardStan]

Now if the Pandora could run SDXC cards that would make my day (2tb storage on a portable device *drools*), until then 2 class 6, 16gb SDHC's will have to do

We won't be hitting 2 TB for a long, long time. I will eat my hat if we don't see a Pandora2* before SDXC cards larger than 256GB.

*offer void if OpenPandora dies before a Pandora2 can be produced.

 

[Viral18]

Now if the Pandora could run SDXC cards that would make my day (2tb storage on a portable device *drools*), until then 2 class 6, 16gb SDHC's will have to do

We won't be hitting 2 TB for a long, long time. I will eat my hat if we don't see a Pandora2* before SDXC cards larger than 256GB.

*offer void if OpenPandora dies before a Pandora2 can be produced.

Haha, I know but a man can dream... I guess we'll have to make sure SDXC compatability ends up in the feature requests for the 'Pandora2', for a bit of futureproofing. XD

 

[DaMummy]

by the time 2tb sdhx come out, there will be a 3d pandora like all the new TVs

 

[Pleng]

I'm looking forward to the day's we're looking back at the SDXC cards and laughing because they called 2Tb 'extreme' capacity!

 

[elwing]

I'm looking forward to the day's we're looking back at the SDXC cards and laughing because they called 2Tb 'extreme' capacity!

"640 k ought to be enough for anyone"...

 

[WizardStan]

"640 k ought to be enough for anyone"...

That was an improvement. IBMs original design left you with only 512k. Bill had to fight to get that extra 128K.

 

[Grench]

And today on Engadget...

http://www.engadget.com/2010/01/13/toshiba-demonstrates-64gb-sdxc-pledges-spring-release/

Skip the SDXC stuff - take a look at the labels on the two SDHC cards in the photo.

R60 - W35 MB/sec

Those probably won't be cheap - yet.

If that is a sign of things to come though, and if I understand the nomenclature of the speed class ratings...

Wouldn't those be 'speed class 35' if such a class existed?

Good times.

 

[bzar]

Now if the Pandora could run SDXC cards that would make my day (2tb storage on a portable device *drools*), until then 2 class 6, 16gb SDHC's will have to do

We won't be hitting 2 TB for a long, long time. I will eat my hat if we don't see a Pandora2* before SDXC cards larger than 256GB.

*offer void if OpenPandora dies before a Pandora2 can be produced.

I'll hold you to that, promise sigged Please make a video.

 

[cobaltage]

FYI: According to Engadget, Samsung has just announced the first 32GB micro SDHC card, which could result in a price drop on lower capacity micro SDHC cards, whenever it is actually released.

http://www.engadget.com/2010/01/13/samsung-announces-64gb-movinand-flash-32gb-microsd-card/

Given the number of portable devices using micro SDHC, and the current lack of a smaller sized flash mem card, micro SDHC with an SD adapter is a good choice for the Pandora, although of course more expensive than SDHC.