SanDisk Extreme 30MB/sec only 20MB/sec? (SD CLASS 10 8GB)

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Olphus

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I got the SanDisk Extreme 30MB/sec Secure Digital Card (SDHC) CLASS 10 - 8GB
which is supposed to give me 30MB/sec but according to
h2testw_1.4 it's ~16MB/sec and
CrystalDiskMark3_0_1b read 20MB/sec
(I repeated the tests at least three times on both apps.)

The card was bought from amazon and it says on the card itself that its 30MB/sec, am I missing something:help:
 
How are you testing it? The hardware that tests it will also have a bearing on speed...
 
gridlock said:
Was it proper Amazon or someone on Amazon Marketplace?

You can ask Sandisk to check for fakes. See http://kb.sandisk.com/app/answers/detail/a_id/1953
Click to expand...

It was "Sold by: Amazon's Jersey Merchant, Indigostarfish.com"
Mine didn't come in an original cardboard packaging just a clear plastic SD protection card case in a padded envelope.
Indigostarfish.com does not appear on the list of authorized SanDisk resellers, but that may not mean much.
The card itself appears legit when comparing it to images online.

"How are you testing it? The hardware that tests it will also have a bearing on speed..."
I'm using a cheap eSecure USB2 card reader. It may be that it can't read above ~20MB/s? I tried another cheap SD reader which I inserted in the USB3 port instead just to test but the results were the same.
 
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Not all SD cards are made equal. Test with an ExpressCard adapter or something similar, as USB 2 can be rubbish especially if lots of small files are involved.
 
Also depends on the file you are transferring. Smaller files are slower than very large files.

Try transferring a 2Gb file and see what speed you get
 
Hang on.. I just re-read the original post. You have a class 10 SD card. Class 10 is 10Mbytes/sec guaranteed, so you're already doing well (see: http://en.wikipedia.org/wiki/Secure_Digital#Speed_Class_Rating) no matter what the marketing claim is. Also, unless you're using a USB3 peripheral, it will still act as a USB2 device so you won't get any difference in speed between the two ports.

So... I just used CrystalDiskMark to test a couple of CompactFlash devices: 30MBy/s Sandisk and 60MBy/s Sandisk bought from reputable retailers. They are tested with the Lexar CompactFlash UDMA card reader. I get (for 2G files)

These are Compact Flash cards.
60MB/s card: sequential read 28.1MBytes/sec, Write 27.1MBytes/sec
30MB/s card: sequential read 27.6MBytes/sec, Write 28.3MBytes/sec

I'd say that means the card reader/USB transfer speeds are limiting the transfer.

I also have a 7-day shop class 10 SD card with speeds of "up to 20MBy/sec". which gives:

Class 10 SDHC card: sequential read 17.4MBytes/sec, Write 12.0MBytes/sec

Take from that what you will. My conclusions are that: 1) on USB 2 with the Lexar reader, you're limited to ~28Mbytes/sec whatever speed the card is. 2) The cheap 7-day shop SDHC card is actually pretty good!
 
arad85 said:
Hang on.. I just re-read the original post. You have a class 10 SD card. Class 10 is 10Mbytes/sec guaranteed, so you're already doing well (see: http://en.wikipedia.org/wiki/Secure_Digital#Speed_Class_Rating) no matter what the marketing claim is. Also, unless you're using a USB3 peripheral, it will still act as a USB2 device so you won't get any difference in speed between the two ports.

So... I just used CrystalDiskMark to test a couple of CompactFlash devices: 30MBy/s Sandisk and 60MBy/s Sandisk bought from reputable retailers. They are tested with the Lexar CompactFlash UDMA card reader. I get (for 2G files)

These are Compact Flash cards.
60MB/s card: sequential read 28.1MBytes/sec, Write 27.1MBytes/sec
30MB/s card: sequential read 27.6MBytes/sec, Write 28.3MBytes/sec

I'd say that means the card reader/USB transfer speeds are limiting the transfer.

I also have a 7-day shop class 10 SD card with speeds of "up to 20MBy/sec". which gives:

Class 10 SDHC card: sequential read 17.4MBytes/sec, Write 12.0MBytes/sec

Take from that what you will. My conclusions are that: 1) on USB 2 with the Lexar reader, you're limited to ~28Mbytes/sec whatever speed the card is. 2) The cheap 7-day shop SDHC card is actually pretty good!
Click to expand...
I know that Class 10 means 10MB/sec guaranteed, but why would Sandisk advertise 30MB/s if it didn't do 30MB/s? I will have to contact Sandisk and hear what they have to say.
I think your conclusion is correct, any USB2 card reader is limited to below the 30MB/s ceiling.
It looks like I might have to buy an USB3 card reader.
 
Olphus said:
but why would Sandisk advertise 30MB/s if it didn't do 30MB/s?
Click to expand...
Because they are hardware manufacturers and will quote maximums. I'm sure, in a lab, with optimised writing hardware and software, it will do 30MBytes/sec. Whether it will do it with your camera/card reader is an entirely different matter...
 
arad85 said:
I'd say that means the card reader/USB transfer speeds are limiting the transfer.
Click to expand...

I'd say you're correct.

And your Lexar reader is one of the fastest USB2 readers in existence. My guess is that the OP is using something slower (although I'll bet a fiver it's still labelled 'High Speed' or similar).

Using CrystalDiskMark is the best way to measure the speed, because it's only the speeds of the card, reader and interface that affects the result.
 
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