Unboxing and review of SanDisk 64GB microSDXC High Endurance Card

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…

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…

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eMMC Adventures, Episode 1: Building my own 64GB memory card with a $6 eMMC chip

As seen on Hackaday!

There’s always some electronics topic that I end up focusing all my efforts on (at least for a certain time), and that topic is now eMMC NAND Flash memory.

Overview

eMMC (sometimes shown as e.MMC or e-MMC) stands for Embedded MultiMediaCard; some manufacturers create their own name like SanDisk’s iNAND or Hynix’s e-NAND. It’s a very common form of Flash storage in smartphones and tablets, even lower-end laptops. The newer versions of the eMMC standard (4.5, 5.0 and 5.1) have placed greater emphasis on random small-block I/O (IOPS, or Input/Output operations per second; eMMC devices can now provide SSD-like performance (>10 MB/s 4KB read/write) without the higher cost and power consumption of a full SATA- or PCIe-based SSD.

MMC and eMMC storage is closely related to the SD card standard everyone knows today. In fact, SD hosts will often be able to use MMC devices without modification (electrically, they are the same, but software-wise SD has a slightly different feature set; for example SD cards have CPRM copy protection but lack the MMC’s TRIM and Secure Erase commands. The “e” in eMMC refers to the fact that the memory is a BGA chip directly soldered (embedded) to the motherboard (this also prevents it from being easily upgraded without the proper tools and know-how.

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Teardown/review of Silicon Power 8GB 200x CompactFlash memory card

Hooray for nice hand-me-down SLR cameras! I finally have a better camera than the one built into my (now ancient) Samsung Galaxy S II that I use for pictures on this blog. The camera, a Canon EOS 50D, had an 8GB CompactFlash card that I was preparing to erase and reuse, and had problems trying to read out the card’s contents; a few stubborn files would refuse to copy and Explorer would simply hang until I restarted the program or unplugged the card. Additionally, when using my Hard Disk Sentinel program to do a surface scan, it too would freeze when reading a certain sector on the card.

Instead of using a USB-to-CompactFlash adapter (I could not find my card reader and have not seen it for over a year now, come to think of it) I used a CompactFlash-to-PATA adapter, then a PATA-to-SATA adapter so I could directly hook up the card to my computer. In addition to having greater theoretical throughput, it allows me to view the S.M.A.R.T. diagnostic data that the card provides.

Memory card issues and performance

The diagnostic information doesn’t really provide any insight into the health of the card; none of the S.M.A.R.T. attributes are listed as critical, and many of them are listed as vendor-specific. Oh well, at least it gave me some sort of information…

After finding a copy of the card’s contents on my home server (I seem to have previously backed up the card before the corruption occurred but didn’t recall doing so until I had raked through some of my archives), I decided I’d do a full card erase and see if it would cause the card to be usable again. I called up the Surface Test in Hard Disk Sentinel and used its surface-write tool to erase the user-accessible area of the card. A few blocks seemed to write dramatically slower than the rest and repeated write tests did not resolve their sluggishness; I call shenanigans with the memory card’s controller and its reluctance in reallocating problematic sectors…

The card itself isn’t very fast. The sequential I/O of the card is good enough for casual photography, but I would definitely not use this card in an embedded system that uses a CompactFlash as a sort of mini-SSD; even though it shows up in my system as a hard drive (non-removable), its random I/O is quite sluggish and its random write speed is worse than that of a standard hard disk drive.

Teardown

The card itself is a sandwich of aluminum plates, a plastic case and the PCB assembly that holds the controller, Flash memory and the CompactFlash connector. A hobby knife run under the aluminum plate was able to separate the plate from the plastic body; some glue and a couple clips were the only things holding the card together.

The card’s controller is a Phison PS3006, which sports a PCMCIA (and therefore CompactFlash) interface with True IDE (or plain PATA) support. It contains an 8051 microcontroller core with a few components to assist with interfacing with the Flash memory, such as a hardware ECC (error correction code) engine and a small amount of SRAM for a buffer.

The datasheet for the PS3006 doesn’t provide information on the S.M.A.R.T. attributes, nor does it indicate what type of Flash wear-leveling is provided. Given the controller’s limited computing capabilities, I’m thinking it uses a less-complex but less-reliable form of wear leveling, known as dynamic wear leveling (see Micron’s application note for more information). It’s less capable of dealing with memory wearout, but doesn’t require the computing overhead of static wear leveling (which proper SSD controllers use to keep performance up).

The memory is an Intel 29F32G08AAMD2 device, which is an asynchronous MLC NAND Flash memory chip. There are two installed on this card with another two footprints on the PCB being unpopulated, suggesting that the 16GB version of this card has all four footprints populated.

Conclusion

Given the simplicity of the card, I don’t really have much else to add about this card. Either way, it’s lost my trust with regards to holding my photos. I bought a NOS Disk 16GB CF card from Amazon as well as a SanDisk Extreme 32GB, and plan to use the latter to hold my photos, with the former mainly being a simple curiosity of the construction of a card from a lesser-known manufacturer. Hopefully those will also provide S.M.A.R.T. data, as I prefer Flash-based storage devices with some sort of S.M.A.R.T. data capability. (Is it an insatiable thirst for knowledge? A means of doing regular ‘check-ups’ on my storage device? Probably the latter, but maaayyyybe the former as well. 🙂 )