I have two SDSDB-8192 cards which have “class 4” on the sticker.
I noticed my camera giving an error with video, and even image storing taking longer.
On putting each of them in a PC, I noticed that the read performance is closer to 1MB/s instead of the expected 4MB/s on BOTH cards. .
I verified that PC setup properly detects read performance of 4MB/s from both the HP L2531A that was in the camera and a Kingston 2GB microsd.
I purchased these from a major retailer. Is there a chance that these could be fakes?
Is there an official way to verify these cards are performing to their labelled specification?
how are you testing the cards? you can use a free app called ATTO benchmark to test the speed of the cards. read and write performance should be at least 4MB/s
I can’t figure out to see how to get random reads with ATTO… it just gives one set of numbers that appear to match the sequential numbers from CrystalDisk mark
I managed to get a Sandisk 8GB card from a different lot for comparison as well.
Sandisk 8GB (marked class 4 - one of the “problem” ones)
0.5 1061 1337
1.0 1983 2037
2.0 3076 4005
4.0 4035 5377
8.0 4349 7249
16.0 4942 8070
32.0 5144 8965
64.0 5234 9269
128.0 5221 9348
I have a set of Sandisk Class 4 SD cards which have random read times of 1MB/s, and one identical looking Sandisk class 4 SD card which is about 4MB/s random read.
I can’t exchange the opened SD cards at the retailer. Can someone confirm that I can RMA these cards, or is this sort of variance expected?
here is the definition of SD class rating from sdcard.org. Nowhere i can see that class rating refers to random read/write so i would say since the cards meet 4MB/s in your ATTO benchmark then no RMA would not be possible. also depending on the technology used in the card performance can vary.
There are two kinds of Speed Class, “Speed Class” and “UHS Speed Class.”
As a characteristic of flash memory, actual transfer speed varies. Variable speeds are difficult to reliably record streaming content such as video because it requires a constant writing speed. Speed Class and UHS Speed Class provide the constant speed necessary for video recording by designating a minimum writing performance so that minimum and constant speed is guaranteed for camcorders, video recorders and other devices with video recording capabilities under the conditional write operation specified in the specification.
Speed Class, designated as Class 2, 4, 6 and 10, is designed for normal and high speed bus interface (mode) and UHS Speed Class 1 is designed for UHS-I bus interface*. (Speed Class and the UHS Speed Class are not compatible.)
