SanDian Extreme PRO 128GB

  • Obtained from: AliExpress
  • Price paid: $5.22
  • Advertised capacity: 128GB
  • Logical capacity: 134,218,776,576 bytes
  • Fake/skimpy flash: Fake flash
  • Protected area: 0 bytes
  • Speed class markings: U3, V30, A2
  • CID data:
    • Manufacturer ID: 0x00
    • OEM ID: 0x0000
    • Product name: 0x4150505344 (ASCII: APPSD)
    • Product revision: 0x00
Card #123Average
Physical capacity32,193,277,440 bytes32,054,865,408 bytes33,894,067,712 bytes32,714,070,186 bytes
Manufacture dateAug 2017Aug 2017Aug 2017N/A
Serial number0x128000050x128000000x12800002N/A
Sequential read speed (MB/sec)16.7315.1816.0115.97
Sequential write speed (MB/sec)8.927.0910.738.91
Random read speed (IOPS/sec)490.391,200.131,107.44932.65
Random write speed (IOPS/sec)0.490.380.360.41
Read/write cycles to first error101519439310
Read/write cycles to complete failure869618981823
Total days to complete failure83469173
Card reader usedJJS CR-UTC4ACJJS CR-UTC4ACTogconn TOG-SD-CRN/A
Package frontN/A
Package backN/A
Card frontN/A
Card backN/A


SanDian is a name that came up fairly frequently in my AliExpress searches, and it was pretty apparent that they were trying to rip off SanDisk — from the product lineup names (“Ultra”, “Extreme”, “Extreme PRO”), to the similar visual design (with the red/black stripes), to the logo (which copies the styled “nD” from SanDisk’s logo). Seeing as how they had several options to choose from, I decided to order a few of each one — in the 128GB and 1TB denominations. However — and I’m going to bury the lead here — they didn’t hold a candle to SanDisk (at least so far).

Initially I was going to lump them into the “off-brand” category; however, given just how closely they’re copying SanDisk’s design, I decided to re-categorize them as knockoffs.

I found it interesting that these cards came in a package that appeared to be for a USB cable rather than the normal clamshell packaging that most SD cards come in.

This is another instance of a seller who set the manufacturer ID and OEM ID to all zeroes to mask their identity and/or the identity of whoever manufactured these cards for them. If the remainder of the CID data is to be believed, then it would mean that these cards were over 6 years old by the time they made it to me. I did manage to find a SanDian store on AliExpress, but their front page made it appear that they were selling women’s clothing — and to boot, they had no actual products listed at the time I looked. This might mean that the SanDian name is being retired (and/or the seller has gone out of business) and that sellers who purchased their cards are simply trying to offload their remaining inventory.

Another thing I found interesting was that physical capacity differed between the three samples. Honestly, I’m at a loss to explain this.

Performance was pretty abysmal, with all metrics being well below average. Even when compared to other fake flash cards in my collection, scores were below average — with the exception of sample #1’s sequential read speed (which was only slightly above average) and sample #2’s random read speed (which was just shy of one standard deviation above average). Performance was not good enough to qualify for any of the speed class markings this card carried. I’ll add my standard “perhaps this card would have performed better if it had been tested under proper conditions” disclaimer, but I highly doubt it would have done much better. Honestly, I would have expected more from a card labeled “Extreme PRO”. Much more. But then again, this is a knockoff brand.

On the endurance front, things are not looking good here either. None of the three samples made it 2,000 read/write cycles — or even 1,000 read/write cycles — before encountering errors.

Sample #1’s first error was a series of bit flip errors affecting two sectors during round 102. It made it 869 read/write cycles before it decided to stop responding to commands. By this point, it had been struggling to stay alive: over 40% of the sectors on the device had been flagged as “bad”, and it went through a couple different phases: one where it disconnected itself from the reader multiple times a day (and had to be unplugged and plugged back in), and one where it would experience long strings of I/O errors before just deciding to work normally again. Finally, though, during round 870, it disconnected itself from the reader and refused to start working again when reconnected — at that point, I decided to declare it “dead”.

Here’s what Sample #1’s progression looked like:

Sample #2’s first error was a series of bit flip errors affecting about 3,400 sectors during round 521. The problem became progressively worse over the following rounds of testing, reaching the point where about 4.27% of the sectors on the device had experienced errors. It finally stopped responding to commands during round 619. Here’s the graph of what this progression looked like:

Sample #3’s first error was a series of bit flip errors during round 440. Like the other two, it slowly deteriorated to the point where over half the sectors on the device had been flagged as “bad”. Here’s what the progression for this sample looked like:

My overall assessment of these cards? Don’t buy them. They perform horribly, not a single one made it even halfway to my 2,000 read/write cycle goalpost, and they’re fake flash to boot. With a little bit of digging, you can find cheaper name-brand cards that are more reliable, have greater capacity, and have way better performance. (Case in point: the Samsung EVO Plus 64GB.)

April 18, 2024

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