Verifying SD Cards

Not a problem. I use h2testw for speed testing, but there are more comprehensive tests available too.

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Cheers, 
David 
Web: http://www.satsignal.eu

Hi rickman,

Really good price. I got some similar few month ago in Germany. 4 of 7 where fake-SD with 8 to 16 GB but unuseable because the flashcontroller disturbes the card while repartitioning (with this trick I got some older fakes to work at least the available flash)

No problem here. Do you really got SDXC speed? Mine are much slower. Don't matter for me, but it ist fake, too.

Marte

I was reading something about being able to reprogram them back down to their "real" size, but it required a special manufacturer's burner thing, not sure if it was hardware or software.

I just completed the H2testw pass and here are the results.

Warning: Only 61052 of 61053 MByte tested. Test finished without errors. You can now delete the test files *.h2w or verify them again. Writing speed: 20.8 MByte/s Reading speed: 38.2 MByte/s H2testw v1.4

I really don't get the price. It is half the price of anyone else. It does not come in a retail package. Maybe they fell off a truck? I'm ready to order five more, but the guy isn't responding.

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Rick C

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Silicon Power Elite 64GB microSDXC Flash Memory Card with Adaptor

$13.50

I was going with the Samsung EVO plus because it rated highly in speed. Any idea how fast this card is?

I haven't found software to measure card speed with other than the H2testw tool. The original tests I was reading were done on the rPi with linux tools. I'll try duplicating those if I can figure out how to make this card bootable on the Pi.

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Rick C

Pretty good, but unless you need 100s of them I'd stick with name brand cards with known good performance for a few bucks more:

See here:

Does the Pi have a version of 'Bonnie' to run? Ive used that for RAI testing in the past.

Cheers

So you think it is better to pay $18.99 for a Samsung EVO+ 64 GB rather than paying $11.50 for a Samsung EVO+ 64 GB?

That was the article I read that shows the EVO+ to be near the top of the heap.

Funny though, he got 18.45 MB/s and 14.0 MB/s for read and write respectively on a 32 GB card while my 64 GB card shows 38.2 and 20.8 in comparison using a PC. That's why I want to run tests on a Pi, so see if that is the difference or if the 64 GB card is faster than the 32 which I doubt. But who knows, maybe the 64 GB card has two chips that run in parallel.

I found a 128 GB card for just $8 with free shipping, but this one *has* to be fake. I've got to buy it to see. The really funny part is the guy is limiting you to just buying one every 10 days. What's *that* about? I'm thinking he doesn't want the nearly certain blowback from one guy buying a bunch of cards and them being crap. He'd rather sell one each to a bunch of people most of who may not notice they were conned until after his check has cleared. I won't be one of those, lol.

In researching how to test for fake cards, one page had a quote from a vendor that he had plenty of happy customers, regardless of the fact his cards were fake and ripping off so many including the brands he was copying.

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Rick C

The Newegg page says its "up to" Read Speed /may/ be way faster than your Samsung.

Speed Class Rating: UHS-I / Class 10 Read Speed: Up to 85 MB/s Class 10 video recording performance

should have more to say about it.

The $11.50 card you got is an EVO+? Hmm, you didn't mention that earlier. It's interesting and I wonder if it's real. There could be another level of fakery: you could conceivably have gotten an actual

64GB card that was not an EVO+. I don't know what's happening with the EVO+ cards though: prices are all over the place.

Yep, or alternatively test a 32GB card on your PC. Comparative tests are way more believable if they're on the same hardware.

I wouldn't. I already know what to expect ;-)

Yes, I saw Best Buy have the best price of $9.99 or so on a 32 GB EVO+. I figured rather than order it on Friday and get it later next week, I'd go to the store when it was convenient on Monday. By Monday it was $14.99, the staff told me it had been on sale. I found the web site prices (including Best Buy selling on eBay) to also be $14.99, lol. But it was *still* on sale with a "regular" price of $25 or so.

I don't care so much about the speed on the PC since it will be used on the Pi. Many things affect the speeds, so testing on the PC is not really important to me.

If it is fake, I'll just complain and they will refund my money or I'll refute the charge on the credit card. Partly I want a chance to examine a fake card. Maybe I shouldn't ask for my money back since I'll be getting what I expect, lol.

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Rick C

I think it was $11 at Adorama last time I looked.

"If"? ;-)

Not a great idea to do a chargeback unless you really have to. Like landlord disputes, having a history of them tends to work against your interests even if were are in the right about the underlying issues.

Fair enough ;-)

Like *that* is a meaningful number!

Where do you think Newegg got their info? I don't see any useful info on the maker's website.

I did find a review that had a benchmark on a PC where they actually saw read speeds of 74 MB/s. But the small block read/writes are significantly slower than on the EVO+. I'm not clear on which is more important and the benchmark should be on the platform of interest for it to truly relevant. So this card may be faster than the EVO+ in some ways, but slower in others.

Maybe I'll get one of these and compare them.

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Rick C

Lol

My interests with *whom*? But now you mention that, I'll use a different card than the one I usually use online.

No, I may be expecting a fake card, but it is unlikely to be usable since on these fakes which are actually smaller than they report, writes to the memory that doesn't exist often craps on the lower memory that is actually there. I don't feel at all guilty making the guy loose some money on the deal. He's actually a criminal hurting both his buyers and the makers of genuine cards.

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Rick C

I'm told it's reported back to credit agencies so affects your general credit score, though at a certain point you might not really care.

Told by whom? In general, the credit score formula is not revealed and I've never seen anything to indicate this. If this were true, it would have to *show* in your credit report. I did a google search and found more than one page that says the opposite, disputing charges on your credit card will *not* damage your credit.

It's best not to spread rumors and other BS if you don't know it to be true.

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Rick C

Oh yeah, that review was on the 128 GB card. Another review on the 64 GB card used H2testw and saw 59 and 21 MB/s for reading and writing respectively, about 50% faster on the read and about the same on the write compared to the EVO+ 64 GB card I measured. They also used the program CrystalDiskMark which the 128 GB reviewer used and got vaguely comparable results, but it doesn't look like they used the same test configuration so hard to tell.

Newegg has the 128 GB version for $28.80 with free shipping. I'm feeling adventurous so I'm going to get it. Funny that all the search results say the Newegg price is a bit higher than what I find on the Newegg page. I guess there was a very recent price drop.

I'll see if I can bench mark the various cards I end up with and report the results.

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Rick C

(Note - I haven't tried any of this, but it is how I would expect to test such a card. I really hope my suggestions don't break your card or anything else, but as I say, it is untested. And be /really/ careful to make sure you use the right block device names!)

You are going to be using the card with the rPi, and that means Linux. You might find it more convenient to test on a PC with a USB card reader.

Your obvious first test is then:

hdparm -t -T /dev/mmcblk0

(to test read speeds).

To check that the card /really/ supports 64 GB, there is only one good way - write 64 GB to it, read it back, and compare the results. That means you first need a file of at least 64 GB that contains a variety of data. You can make a nice one like this:

dd if=/dev/urandom of=sampleFile bs=1M count=65536

But you could also just attach a USB hard drive of at least 64GB, with a whole bunch of data on it. Just make sure the filesystem on the drive is not mounted - you don't want it to change during the test.

Write your file to the SDCard:

time dd if=sampleFile of=/dev/mmcblk0 bs=1M count=65536

or

time dd if=/dev/sdb of=/dev/mmcblk0 bs=1M count=65536

(Assuming the USB drive is on /dev/sdb)

The time output will let you calculate the sequential write speed, and any errors might show you that the size is less than 64GB

Then compare the data written to the original:

time cmp sampleFile /dev/mmcblk0

or

time cmp /dev/sdb /dev/mmcblk0

If you get a message saying the files differ, that shows the limit of working flash.

This process not only checks that the card is not fake, it also checks that it is not damaged or worn out.

Then you can start using card. If you are using it exclusively for the Pi, you can use a proper filesystem rather than NTFS or exFAT. ext4 works fine, but for something smarter you can use btrfs along with lzo compression and "dup" to save you from bit errors. Remember also that with Linux, you can partition your SDCard if you want.

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If you are using a UHS-1 card in a normal SDHC or SDXC reader you wont see the full performance. You need a UHS-1 capable USB3 reader to benchmark them on a PC. The Raspberry Pi isn't UHS-1 so wont get as high a speed.

---druck