Checking relative write and read speeds on some 32GB μSD cards
The video above is cropped from a 1080p (i.e. 1920×1080-pixel) AVI video recorded by a cheapo trail cam I purchased recently out of curiosity. These things have myriad potential uses, including seeing which of your cats prefers which flavor of wet and or dry cat vittles and how much water each animal is really drinking.
Poking around inside and looking up the markings on the brainiest-looking component on the PCB, I found that IC was a Vehicle Camera Recorder SoC
manufactured by a Taiwanese company called Generalplus for applications like, aside from my trail cam, vehicle dash cameras.
It records to an owner-provided μSD card and can accommodate cards with capacities up to 32GB. We had larger-capacity cards (e.g. 256GB and 512 GB) and dinky little 2GB cards on hand, but nothing in between, so I got some from Taobao.
Two of them are UHS Speed Class
#1 (corresponding to a promised write speed of at least 10 MB/s) and two are UHS Speed Class
#3 (minimum write speed of 30 MB/s). The UHS speed ratings are the ones I’m accustomed to considering, but there are other write-speed rating schemes. You can see the Speed Class page at sdcard.org for more), but I’ll blather a bit about the subject here. There’s an older Speed Class
ratings system (the numbers in nearly-closed circles) that goes thusly: 2, 4, 6, 10 (in MB/s). It tops out at 10 Mb/s and any card faster than that manufactured by a company like SanDisk which still prints those ratings marks on their cards will be a ten-in-semicircle. Video Speed Class
is more recent and goes V6, V10, V30, V60, and v90 (also in Mb/s) and it supersedes UHS ratings in the same way that they supersede SC semicircled ratings. A v90 μSD card, suitable for recording 8k video, may be printed with a UHS 3 ratings symbol, but the manufacturer is promising a write speed of 90 Mb/s or higher.
When I got these cards, I looked online for a tool to test their write and read speeds and downloaded and used MediaTester, a project of Doug Krahmer. The cards were connected to a USB port on a PC using a USB3 no-name μSD/SD adapter USB dongle.
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They all appeared to meet or exceed their ratings. The second-slowest card, the Samsung Pro Endurance, is marked U1 (UHC class 1) but appeared to squeak past the 30 Mb/s threshold for U3. The fastest (at 84+ Mb/s) of these four cards, the SanDisk High Endurance, could have been marked V60 rather than V30.
Take the numbers above with a grain of salt. They’re just-for-funsies measurements, from single runs on a single computer, and without any effort to account for hypothetical overhead from the adapter or the computer hardware or to confirm the accuracy of the values produced by the testing software. Perhaps the performance of the cards themselves degrades over time and through use rapidly and significantly enough that they won’t actually outperform their printed write-speed ratings very much or for very long.
Unless and until I have a pressing need to do a deep dive on μSD card performance and performance measurement, this is good enough for me for now. Big-co V60 and v90 SD cards are readily available (at least I see them from SanDisk) but v60 and v90 name-brand μSD cards seem to be thin on the ground. There are some μSDs stamped v60 or v90 from unfamiliar brands (e.g. US-based Delkin Devices and a slew of new-to-me Chinese companies) and I may obtain some of them for a quick test.
UPDATE: V60 μSD speed test (sample size of one)
Here’s the test results for a 128GB MOVESPEED (aka Shenzhen Speedmobile Technology Co., Ltd) stamped with a V60 rating:
The MOVESPEED μSD’s average write speed was 75.6 Mb/s, so it comfortably exceeded the v60 rating threshold whilst being slower than the SanDisk High Endurance (which clocked in at 84.3 Mb/s).
The card bears markings for Speed Class 10, UHS Speed Class 3, and Video Speed Class 6. The prominent A2
mark indicates a claim that it meets Application Performance Class 2 (aka A2 class) standards around speeds for random IOPS. The APC stuff seems oriented towards concerns about the peppiness of running software stored on μSDs or their use as add-on memory for devices that might have multiple pieces of software writing to and reading from the card simultaneously. Of the other 4 cards shown in this post, only one bears an APC rating, the A1
-marked SanDisk Ultra.
In case it’s of interest to anyone, I’m including a snapshot of the model/serial number section of the back side of the since-discarded packaging for this card below.
Selected details from the white sticker with the bar code:
| Product name: | H300 |
| Model number: | YSTFH300-128GU3 |
| Production date: | 20230614 (June 14th, 2023) |