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Confused @ Evo Plus and Evo Pro Plus A2 ratings

(Topic created on: 08-01-2023 01:57 AM)
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rolyantrauts
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If I go on https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/

A class 1 (A1) card is specified by 1500 IOPs minimum random read and 500 IOPs minimum random write

A class 2 (A2) card is pecified by 4000 IOPs minimum random read and 2000 IOPs minimum random write

I started with a 128gb Evo Plus (white) but I am totally confused by the A2 rating due to what even a generic A1 from mymemory can provide.

Here is the 32gb Mymemory generic A1
[Read]
SEQ 4KiB (Q= 8, T= 1): 11.049 MB/s [ 2697.5 IOPS] < 2961.29 us>
SEQ 4KiB (Q= 1, T= 1): 9.881 MB/s [ 2412.4 IOPS] < 413.64 us>
RND 4KiB (Q= 32, T= 1): 7.464 MB/s [ 1822.3 IOPS] < 17518.72 us>
RND 4KiB (Q= 1, T= 1): 6.534 MB/s [ 1595.2 IOPS] < 625.05 us>

[Write]
SEQ 4KiB (Q= 8, T= 1): 4.771 MB/s [ 1164.8 IOPS] < 6855.69 us>
SEQ 4KiB (Q= 1, T= 1): 4.964 MB/s [ 1211.9 IOPS] < 824.34 us>
RND 4KiB (Q= 32, T= 1): 4.675 MB/s [ 1141.4 IOPS] < 27938.02 us>
RND 4KiB (Q= 1, T= 1): 3.966 MB/s [ 968.3 IOPS] < 1030.37 us>

Here is a EvoPlus 128gb (white) A2

[Read]
SEQ 4KiB (Q= 8, T= 1): 13.969 MB/s [ 3410.4 IOPS] < 2326.91 us>
SEQ 4KiB (Q= 1, T= 1): 12.428 MB/s [ 3034.2 IOPS] < 329.03 us>
RND 4KiB (Q= 32, T= 1): 11.271 MB/s [ 2751.7 IOPS] < 11601.40 us>
RND 4KiB (Q= 1, T= 1): 10.004 MB/s [ 2442.4 IOPS] < 408.77 us>

[Write]
SEQ 4KiB (Q= 8, T= 1): 3.386 MB/s [ 826.7 IOPS] < 9657.65 us>
SEQ 4KiB (Q= 1, T= 1): 3.272 MB/s [ 798.8 IOPS] < 1248.77 us>
RND 4KiB (Q= 32, T= 1): 3.508 MB/s [ 856.4 IOPS] < 37161.91 us>
RND 4KiB (Q= 1, T= 1): 3.205 MB/s [ 782.5 IOPS] < 1274.52 us>

Not only does it not meet A2 spec its considerably slower on random writes than a A1 card?
So that got me thinking maybe this card isn't bonfied and I purchased a EvoProPlus 128gb that comes with a samsung usb 3.0 card reader.


Here is a EvoProPlus 128gb (blue) A2

[Read]
SEQ 4KiB (Q= 8, T= 1): 13.458 MB/s [ 3285.6 IOPS] < 2431.09 us>
SEQ 4KiB (Q= 1, T= 1): 11.470 MB/s [ 2800.3 IOPS] < 356.44 us>
RND 4KiB (Q= 32, T= 1): 10.843 MB/s [ 2647.2 IOPS] < 12041.19 us>
RND 4KiB (Q= 1, T= 1): 10.640 MB/s [ 2597.7 IOPS] < 384.47 us>

[Write]
SEQ 4KiB (Q= 8, T= 1): 3.261 MB/s [ 796.1 IOPS] < 10015.06 us>
SEQ 4KiB (Q= 1, T= 1): 3.081 MB/s [ 752.2 IOPS] < 1326.09 us>
RND 4KiB (Q= 32, T= 1): 3.172 MB/s [ 774.4 IOPS] < 41072.57 us>
RND 4KiB (Q= 1, T= 1): 3.137 MB/s [ 765.9 IOPS] < 1301.98 us>

Neither of the cards seem to meet A2 specs but I am even more confused for random writes they are even slower than a generic A1!?

The above was used the samsung supplied with the evo pro card reader windows 10 usb3
Am I doing something wrong with the format of these cards as I am totally confused at the results I seem to be getting.
Surely an A2 card for random writes can not be considerabilly slower than an A1 card?

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Members_X0HNZbq
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From my experiments, I could only reach 65MB/s write (large files) from the Samsung EVOSelect card rated at 130Mb/s (512GB size). Read was just a little higher. Basically, half of the rated speed, still slower than my old USB 2.0 hard drive.

The situation is similar with a competition A2 card rated at 130MB/s write speed. However, that card performs at 116 MB/s (close to rated speed) with their own USB card reader, but not on any of my other readers.

Unfortunately, the Samsung card does not perform better on the above reader that gives good A2 results for the competition. I don't have a Samsung USB PRO reader, maybe that would be able to unleash the full A2 speed for Samsung SD card.

 

Both cards still perform at half the rated speed on a UHS-II reader that is proven to reach way higher speeds with an UHS-II cards.

 

My conclusion: It seems like A2 speed is only reachable in special USB card readers and negotiation might be vendor specific. Not sure if you can really achieve the A2 extra speed using the card in a device having an older reader. Someone say he sees a better write compared with the A1 cards for video capture, I didn't test this.

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