Tag Archives: NAND

Unboxing and review of SanDisk 64GB microSDXC High Endurance Card

Posted on by
3

UPDATE (July 19, 2020): I’ve analyzed a 128GB version of the High Endurance card, and it appears that SanDisk is using 3D TLC Flash.

Dashcams: they can be a crucial tool when reconstructing events in a vehicular incident, or a source of entertainment when watching compilations on YouTube. Like any modern device, they generally use SD or microSD cards as their storage medium. However, not all cards are created equal.

Cheaper cards, like SanDisk’s Ultra lineup, use cheaper TLC (triple-level cell) NAND Flash that is ill-suited to the harsh working conditions of a dashcam. Not only does the card have to endure temperature extremes, the constant writes can burn through the Flash’s write cycles in short order. In fact, SanDisk specifically denounces this line of cards for use in continuous-recording applications.

The solution: high-endurance memory cards! These cards (at least in theory) use more durable MLC or even SLC NAND Flash, which can take many more write cycles. I purchased the 64-gigabyte model, the SDSQQNR-064G-G46A.

Unboxing

The card’s packaging isn’t much different than SanDisk’s typical microSD card offerings. The paper-and-plastic package includes a small blister pack that holds the microSD card itself and the full-size SD card adapter, without a carrying case (granted, the memory card is expected to stay inside the dashcam for most of its working life).

The packaging also includes a license key for a 1-year subscription to the RescuePRO data recovery software (although in all honesty, you’d be better off using the free PhotoRec software instead).

Endurance Rating

SanDisk’s lineup of high-endurance memory cards are designed for use in very write-intensive workloads, such as constant video recording.

Unfortunately, the endurance specifications for these cards are (probably intentionally) vague, only providing a set number of hours of video recording. However, we can infer a rating with a little bit of math.

SanDisk’s card packaging defines Full HD video to be 26 Mbps, which is equivalent to 3.25 (binary) megabytes per second. This equates to 11,700 megabytes per hour, or 11.426 gigabytes per hour. With a rating of 5,000 hours at this data rate, we get a specified endurance of 57,128.91 gigabytes written, or 55.79 terabytes written (TBW).

Memory cards, like other block-based storage media, often define capacities with decimal prefixes, whereas computers usually binary. A “64-gigabyte” card is really 59.605 binary gigabytes (“gibibytes“) in capacity, but in this blog post I’m using the Windows notation of gigabytes; that is, calculating in binary but displaying as decimal. 😛

Therefore, we get a final calculated P/E (program-erase) cycle count of… 936 cycles. This is more in line with traditional 2D TLC NAND Flash, so I suspect that this rating is either based on different bitrates, or SanDisk is being really, really conservative in their estimates – or heck, maybe this really is just TLC NAND Flash that’s being configured and/or warrantied differently by SanDisk. As much as I am tempted to remove the epoxy coating that covers the manufacturing test pads in order to get a NAND Flash signature directly, I like having a warranty for at least a few years. Maybe I’ll buy another card to try this on…

UPDATE (July 19, 2020): I got my paws on another card (the 128GB variant), and did some reverse-engineering work on it to determine what Flash SanDisk used. It turns out they used 3D TLC NAND, which is still quite durable and reliable due to the use of larger process geometries. The Flash should easily withstand thousands of write cycles without much issue.

Card Information

Using an older laptop with a true SD-compliant slot (most newer ones are just USB card readers internally), I was able to grab the card’s metadata from Linux. These information files are found in /sys/block/mmcblkX/device, where X is usually 0 depending on your host machine. Android used to be able to do this as well, but nowadays it’s not possible without a rooted operating system.

Item Value
CID (Card ID) 035744534836344780ed1bbb9e013100
CSD (Card Specific Data) 400e0032db790001dbd37f800a404000
Manufacturer ID 0x03 (SanDisk)
Manufacture Date January 2019
Device Name SH64G
Firmware Version 0x0
Hardware Revision 0x8

Initial Formatting

The card is formatted as exFAT, with a 16 MB offset (that is, the first 16 MB of the card is unallocated), with an allocation unit size of 128 kilobytes. It uses a very basic MBR (Master Boot Record) partition structure, with the first sector being the bare minimum to be recognized as a valid structure.

Performance

Now that I’ve probably irked some of my readers with my usage of decimal and binary prefixes, it’s time to see how fast this card can go. SanDisk’s own ratings for the card are very brief, citing a sequential read/write speed of 100 and 40 MB/s respectively. It is rated for the V30 Video speed classification, which guarantees a minimum of 30 MB/s sequential writes continuously.

All the tests below were performed on my desktop computer using a FCR-HS4 USB 3.0 reader from Kingston, which is based on the Realtek RTS5321 chipset.

CrystalDiskMark

CrystalDiskMark is the de-facto standard for storage benchmarks. I’m using the 64-bit edition of CDM, version 5.2.0.

I/O Type Read Write
Sequential QD32 91.80 MB/s 60.56 MB/s
Sequential 93.33 MB/s 61.66 MB/s
4K Random QD32 8.319 MB/s
2129.7 IOPS		 4.004 MB/s
1025.0 IOPS
4K Random 8.121 MB/s
2079.0 IOPS		 3.971 MB/s
1016.6 IOPS

The sequential I/O speeds are on par with a modern microSDXC card, and the IOPS aren’t too shabby either; they exceed the IOPS requirements for the A1 performance class which requires R/W IOPS of 1500 and 500 respectively. This could make this type of card a viable option for other write-heavy environments – this includes single-board computers (SBCs) like the Raspberry Pi, where memory card failures due to excessive writes are common.

ATTO Disk Benchmark

The card’s read/write performance levels off at around the 64-kilobyte mark during testing, showing that operations smaller than this incur a significant performance penalty. This may also be indicative of the internal page and block sizes of the NAND Flash itself.

Hard Disk Sentinel

Hard Disk Sentinel comes with a bunch of disk benchmarking tools, including some to test the entire “surface” of a drive. I used the software’s Surface Test tool to measure the card’s performance before and after filling the drive with data – first with random data, then with all zeroes.

Random Seek Test

The Random Seek Test measures the card’s latency when performing random “seeks”, although more accurately it reads a single sector from a random location.

State Average Latency Minimum Latency Maximum Latency
Empty/Initial (0x00) 360 µs 350 µs 420 µs
Random Fill 600 µs 590 µs 670 µs
Zero Fill 600 µs 590 µs 690 µs

The card initially had about 420 microseconds of latency, but after filling the card with random data, this increased to 670 microseconds. Filling the card with all zeroes again did not improve performance, and his isn’t helped by the fact that SD cards generally lack the ability to “TRIM” unused sectors like SSDs or eMMC chips.

Full Surface Read (or at least an attempt)

This is where things get a bit… interesting. It was around this time that I noticed some performance inconsistencies that didn’t show up on other benchmarks. Although the I/O speeds largely matched what my other benchmarks revealed, I noticed frequent dips below normal, often down to the mid-20 MB/s range! I wasn’t sure that this was necessarily the card’s fault (pauses in read/writes could result in performance degradation on a device if it can’t buffer the writes well enough), or if my card reader/operating system/etc. was responsible.

I decided to hold off on publishing the sequential write test until I get this issue figured out – perhaps it’s worthy of a blog post all on its own…

Advertisement

Discreet Quality: Review of the sketchiest-looking 512GB Lexar SDXC card

Posted on by
Reply

It’s amazing how much Flash-based storage technology has advanced in the last few years, especially considering how much prices have dropped.

Naturally, when it comes to speed, capacity and price, consumers tend to look for the lowest price; as manufacturers race towards the bottom line, many will take the low road and sell counterfeit goods. This is especially prevalent in the NAND Flash market, and online marketplaces like eBay, AliExpress and even Amazon are fraught with countless fake storage devices that claim high capacities at too-good-to-be-true prices. It’s not uncommon to see unrealistic capacities sold for a few tens of dollars, but what the customer ends up receiving is a storage device with a falsified capacity that will pass a simple copy-paste test but will corrupt itself with extended use.

While browsing eBay for some deals on some Flash storage, I happened upon a very strange-looking 512GB SDXC card. It was listed as an OEM Lexar card but had no labels, selling for an unprecedentedly low price of $60 USD (the card would cost several times more at normal retail outlets). On the outside, everything about the card’s exterior seems to raise a red flag that the card is not to be trusted.

Lexar OEM 512GB Listing

eBay listing of the Lexar OEM 512GB SDXC card

Upon closer inspection, there are some hints that one shouldn’t always judge a book – er, card – by its cover. The laser-etched markings might look like cryptic gibberish to the layperson, but the markings “SM2702BAC” and “L95B” have actual meanings; the SM2702 is an SD card controller by Silicon Motion, and L95B refers to the 16nm generation of MLC NAND Flash by Micron, which owns the Lexar brand (but unfortunately is being discontinued). The seller also says that the cards have been tested, which is reassuring.

I decided to take the plunge and plunk down about $80 USD including shipping (or $105 CAD at the time) and buy a card for myself.

A Closer Look

After waiting a few weeks, the card showed up in my mailbox. The seller did a very good job packaging it, even placing the card in an ESD shielding bag before wrapping it with foam and placing it in a bubble mailer (it’s much better than the plastic wrap I’ve had some used i7 CPUs by a huge amount).

 

Back of the Lexar OEM 512GB SDXC card
Front of the Lexar OEM 512GB SDXC card

The card looks very plain, with the top label area lacking any labeling, and the same laser-etched markings on the back. The card’s contacts indicate that it has been placed in a card reader a few times before (presumably for testing).

Card Identification

I used my old Gateway M-7305u laptop with Kali Linux to see what information the card reports. These older laptops have true SDA (SD Association) compliant card slots, so they will identify as an actual SD card instead of a USB drive like with many modern laptops; in Linux these show up as devices like /dev/mmcblk0 instead of /dev/sda. By using the “dmesg -wH” command I can read the kernel logs once the card is connected to the computer.

[Jan24 10:52] mmc0: new high speed SDXC card at address 59b4
[ +0.094917] mmcblk0: mmc0:59b4       483 GiB 
[ +0.001111] mmcblk0: p1

The card reports a capacity of 483 GiB (that’s binary gigabytes, or 519.6 decimal – a.k.a. “weasel” – gigabytes), but the SD card name is ”     ” – five ASCII spaces. Everything about the card superficially rings alarm bells! However, I wasn’t phased, and decided to try the card in my Kingston FCR-HS4 USB 3.0 card reader, which uses the Realtek RTS5321 chipset.

Lexar OEM 512GB Partition

OEM Lexar 512GB SDXC card in Disk Management

Examining the card in Windows shows that the card was formatted as exFAT with a drive name of “SDXC”, suggesting it may have been formatted by the seller with the SD Formatter tool. Looking at the raw sector data in Hard Disk Sentinel suggests that the seller indeed do a full capacity test, as the data patterns match that of the program H2testw, an excellent tool for detecting fake Flash memory. This is a good sign – the seller did their due diligence and by this point I already had a good feeling that the card is genuine.

However, I wanted to test this for myself, so I ran the H2testw utility myself and let it run on the card. The write speed remained consistent throughout, which is a good indication that the card is not overwriting memory locations like in fake Flash storage (the card did get uncomfortably hot during the process, however). It took four hours to complete the write and read test, but everything came out clean – the card is genuine, even when every other sign says otherwise!

Lexar 512GB OEM H2testw

H2testw verifying that the OEM Lexar card’s 512GB capacity is genuine

Performance

With the card verified, it was time to put it to the test.

CrystalDiskMark

The card showed sequential read speeds of 92.03 MB/s and sequential write speeds of 60.45 MB/s; the sequential write speed coincides with the seller’s rating of 400x (400 * 150 kB/s = 60 MB/s).

The random 4K I/O performance isn’t great, especially with writes, but it isn’t bad either. The card managed 4K random read speeds of 6.644 MB/s (1700.9 IOPS) and 4K random write speeds of 0.671 MB/s (171.8 IOPS).

Lexar 512GB OEM Benchmark

Benchmark of the 512GB Lexar OEM SDXC card in CrystalDiskMark 3.0.4

Conclusion

In the end, I was satisfied – I got a 512GB SDXC memory card at a fraction of the cost from a normal retail outlet. It’s not exactly a speed demon, but it’s not a slowpoke either. The looks may be deterring for most folks (and rightly so), but with the right tools and knowledge, one can pick up one of these less aesthetically-pleasing memory cards and save some serious coin in the process.