SanDisk Ultra 32GB

  • Obtained from: AliExpress
  • Price paid: $6.49
  • Advertised capacity: 32GB
  • Logical capacity: 31,914,983,424 bytes
  • Physical capacity: 31,914,983,424 bytes
  • Fake/skimpy flash: Skimpy (0.27% skimp)
  • Protected area: 83,886,080 bytes
  • Adjusted skimp: 0.0035%
  • Speed class markings: Class 10, U1*, A1
  • CID data:
    • Manufacturer ID: 0x03**
    • OEM ID: 0x5344 (ASCII: SD)**
    • Product name: 0x5344333247 (ASCII: SD32G)
    • Product revision: 0x85

* The U1 marking appeared on the card, but did not appear on the package.

** This manufacturer ID/OEM ID is pretty well known to be associated with SanDisk.

Card #123Average
Price paid$6.49$6.49$7.02$6.67
Serial number0x5ce0bc8b0x5cf0bc890x6f65d36bN/A
Manufacture dateDec 2022Dec 2022Aug 2023N/A
Sequential read speed (MB/sec)83.9692.4886.9387.79
Sequential write speed (MB/sec)23.7624.1532.8126.91
Random read speed (IOPS/sec)3,386.413,777.712,272.083,145.40
Random write speed (IOPS/sec)469.10381.76428.31426.39
Read/write cycles to first error1,9051,5833951,294
Read/write cycles to complete failure2,2094,035Not yet determined3,122
Total days to complete failure15286Not yet determined121
Card reader usedTogconn TOG-SD-CRSanDisk MobileMateJJS CR-UTC4ACN/A
Package frontN/A
Package backN/A
Card frontN/A
Card backN/A


The SanDisk Ultra has been my go-to SD card for a number of years now. I run a farm of single-board computers, and I’ve been primarily using these cards (in the 16GB denomination) as the primary storage device for these devices — and in general, I’ve found them to be cheap and reliable. I’ve had good luck with them, but I wanted to be objective here and make sure that I ran these through the same paces as the other cards in my collection.

Performance-wise, these cards did well in both sequential read and random read/write speeds, but slightly below average in sequential write speeds. Both samples tested so far performed more than one standard deviation above average in random read speeds, with sample #1 performing more than two standard deviations above average. This was enough to merit the Class 10 and U1 markings; however, it fell short of the 500 IOPS/sec of random write performance required for the A1 mark. I’ll throw in my standard “perhaps this card would have done better if it had been tested under proper conditions” disclaimer here — sample #1 was close enough that this may actually be true.

This is another UHS-I card that advertises speeds higher than what should be possible under the UHS-I standard: the package advertises (in Chinese) “speeds up to 120MB/second”. To give this card a fair chance, I tested one of them using one of the SanDisk MobileMate readers, but it didn’t seem to perform significantly better with this reader than it did with the Togconn or JJS readers.

The first error for samples #1 and #2 was an address decoding error. Curiously, both samples died when I plugged new JJS CR-UTC4AC card readers into nearby USB ports — which leaves me wondering if (a) these readers are creating some sort of surge (or brownout) on the USB bus, (b) the particular USB hub where this issue occurred didn’t electrically isolate the USB ports from each other, and (c) the card readers themselves failed to stop the surge from going through to the cards. But that’s just speculation. However, embeddedTS once tested a number of SanDisk cards (though they didn’t specify exactly which model/capacity) and noticed that some of them would fail during a brownout — so perhaps plugging in another reader simply caused a brownout on the USB bus that these cards didn’t like.

Sample #3’s first errors — which occurred during round 395 — were an odd combination: 7 contiguous sectors where the data was shifted by one sector, but also the first four bytes of each sector were all zeroes; followed by 2,048 contiguous sectors where the data was shifted by one sector. It has endured 1,351 read/write cycles in total so far.

June 9, 2024

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