Verifying SD Cards

rickman <gnuarm@gmail.com> writes:
> Yes, I saw Best Buy have the best price of $9.99 or so on a 32 GB
> EVO+. ...  By Monday it was $14.99... "regular" price of $25 or so.

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

> If it is fake,

"If"?  ;-)

> I'll just complain and they will refund my money or I'll refute the
> charge on the credit card.

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.

> 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.

Fair enough ;-)

On 5/4/2016 12:40 AM, Paul Rubin wrote:
> rickman <gnuarm@gmail.com> writes:
>> Yes, I saw Best Buy have the best price of $9.99 or so on a 32 GB
>> EVO+. ...  By Monday it was $14.99... "regular" price of $25 or so.
>
> I think it was $11 at Adorama last time I looked.
>
>> If it is fake,
>
> "If"?  ;-)

Lol

>> I'll just complain and they will refund my money or I'll refute the
>> charge on the credit card.
>
> 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.

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


>> 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.
>
> Fair enough ;-)

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

rickman <gnuarm@gmail.com> writes:
> [chargeback]
> My interests with *whom*?  But now you mention that, I'll use a
> different card than the one I usually use online.

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.

On 5/4/2016 2:55 AM, Paul Rubin wrote:
> rickman <gnuarm@gmail.com> writes:
>> [chargeback]
>> My interests with *whom*?  But now you mention that, I'll use a
>> different card than the one I usually use online.
>
> 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.

-- 

Rick C

On 5/4/2016 12:44 AM, rickman wrote:
> On 5/3/2016 11:40 PM, Dr. Dynamite wrote:
>> On 05/03/2016 01:31 PM, rickman wrote:
>>> On 5/3/2016 3:26 PM, Dr. Dynamite wrote:
>>
>>>> Silicon Power Elite 64GB microSDXC Flash Memory Card with Adaptor
>>>>
>>>> $13.50
>>>>
>>>> http://www.newegg.com/Product/Product.aspx?Item=N82E16820301310
>>>
>>> I was going with the Samsung EVO plus because it rated highly in speed.
>>>   Any idea how fast this card is?
>>
>> The Newegg page says its "up to" Read Speed /may/ be way faster than
>> your Samsung.
>
> Like *that* is a meaningful number!
>
>
>> Speed Class Rating:   UHS-I / Class 10
>> Read Speed:   Up to 85 MB/s
>> Class 10 video recording performance
>>
>> http://www.silicon-power.com/ should have more to say about it.
>
> 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.

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.

-- 

Rick C

On 03/05/16 16:54, rickman wrote:
> 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.
> 

(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.

On 04/05/2016 08:50, rickman wrote:
> On 5/4/2016 12:44 AM, rickman wrote:
>> On 5/3/2016 11:40 PM, Dr. Dynamite wrote:
>>> Speed Class Rating:   UHS-I / Class 10
>>> Read Speed:   Up to 85 MB/s
>>> Class 10 video recording performance

[Snip]

>> I did find a review that had a benchmark on a PC where they actually saw
>> read speeds of 74 MB/s.

[Snip]

> 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,

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

On 5/3/2016 2:33 PM, rickman wrote:
> On 5/3/2016 4:42 PM, Paul Rubin wrote:
>> rickman <gnuarm@gmail.com> writes:
>>> I found an eBay vendor with a really *great* price on 64 GB microSDXC
>>> cards and ordered one ($11.50 shipped).
>>
>> 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:
>>
>>    http://www.adorama.com/ISGMBMC64DAA.html
>
> 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?

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.
>
>
>>> 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?
>>
>> See here:
>> http://www.midwesternmac.com/blogs/jeff-geerling/raspberry-pi-microsd-card
>>
>
> 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.
>

In comp.sys.raspberry-pi Paul Rubin <no.email@nospam.invalid> wrote:
> 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.

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:
https://www.kernel.org/doc/Documentation/mmc/mmc-dev-attrs.txt

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.

http://www.bunniestudios.com/blog/?page_id=1022
is the canonical reference for this kind of fishy-ness.

Theo

On Wed, 04 May 2016 02:24:33 -0700, mike <ham789@netzero.net> Gave us:

>Problem is that you have no way of telling which (if any) is the
>real McCoy.


  There are no McCoy brand memory sticks.