Verifying SD Cards

I found an eBay vendor with a really *great* price on 64 GB microSDXC
cards and ordered one ($11.50 shipped). It was shipped from within the
US so it came in a few days. I've used H2testw to verify that it really
is 64 GB and got this message... "Warning: Only 61052 of 61053 MByte
tested." A dialog pops up saying this is normal if you are using NTFS,
but I formatted it in exFAT. So is this a problem?
The intended use is in the rPi, so I will try firing that up later today
and see if I can run a similar test there. I'd like to verify the speed
of the card. What utility would be good for that?
If the card checks out I'm going to order several more.
--

Rick C
Reply to
rickman
Loading thread data ...
Not a problem. I use h2testw for speed testing, but there are more comprehensive tests available too.
--
Cheers, 
David 
 Click to see the full signature
Reply to
David Taylor
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
Reply to
Marte Schwarz
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.
--

Rick C
Reply to
rickman
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:
formatting link

See here:
formatting link
Reply to
Paul Rubin
Does the Pi have a version of 'Bonnie' to run? Ive used that for RAI testing in the past.
Cheers
Reply to
Martin Riddle
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.
--

Rick C
Reply to
rickman
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 ;-)
Reply to
Paul Rubin
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.
--

Rick C
Reply to
rickman
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 ;-)
Reply to
Paul Rubin
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.
--

Rick C
Reply to
rickman
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.
Reply to
Paul Rubin
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.
--

Rick C
Reply to
rickman
(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.
Reply to
David Brown
I think it's better to pay $18.99 for a Samsung EVO+ 64GB rather than paying $11.50 for one that may have a sticker that says it's a Samsung EVO+ 64GB, but isn't. Problem is that you have no way of telling which (if any) is the real McCoy.
I wrote a little test program that tests for fakeness (less storage than advertised) in a minute or so, but never had any SDXC cards or reader to test it on. Does work on 128GB USB3 sticks.
Back in the 16GB days, I used to take a laptop to pickup Craigslist cards. I disappointed more than a few sellers when I verified that their cards were fake. Don't think I ever found a REAL 16GB flash card locally on Craigslist.
Speed has more than one dimension. I only care about big file transfers for backups and app-install files. Can test that by copying a big file with a program that shows the copy speed. Gets a lot more complex if you care about lotsa small files.
Reply to
mike
On the Pi, have a look around /sys/class/mmc_host/ or /sys/block/mmcblk or a similar location. This gives you parameters from the card itself - here's a list:
formatting link

On a fake, these details are often bogus - for example a serial number of '0' or '99' is suspect, while a serial of '24592839DFSDFJSD' is more plausible (google it. If someone else has the same serial number, something is wrong)
This only works if you have a directly-connected MMC/SDHCI controller - not if the card is attached by USB.
formatting link
is the canonical reference for this kind of fishy-ness.
Theo
Reply to
Theo Markettos
On Wed, 04 May 2016 02:24:33 -0700, mike Gave us:
There are no McCoy brand memory sticks.
Reply to
DecadentLinuxUserNumeroUno
So if you see one you know it's been doctored.
--
Steve O'Hara-Smith                          |   Directable Mirror Arrays 
C:>WIN                                      | A better way to focus the sun 
 Click to see the full signature
Reply to
Ahem A Rivet's Shot
Thanks. When I get my 64 GB card booted on the pi, I'll check the internal info.
--

Rick C
Reply to
rickman
That last sentence is the point. I don't know if any of these cards is the "real McCoy". In researching this I found reports of getting fake cards from mainstream brick and mortar retailers. So who *can* you trust?
I'm more concerned with day to day operations than backups. Backups will likely be done over the network anyway and so will be limited by those speeds.
--

Rick C
Reply to
rickman

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.