Is It Time To Lay Your Memory Cards to Rest? What About the Card Readers?

Hey everyone. A thanks to some readers for the ideas behind this article. Sheila gets credit for the card subject and Andrew for the card reader subject.

Memory Cards

It’s often said and is well proven that whatever you paid for your memory card three years ago, will now buy you at least twice the storage and better performance. The math works. I have checked and you can as well.

The reason you should care is that the memory in memory cards is some form of flash memory. It could be NAND, 3D NAND or if a new card NVME. The memory type will determine maximum storage, and the equally if not more important factor of transport bandwidth.

Replace Your Memory Cards Every Three Years

We spend lots of (too much?) money on cameras and gear but rarely replace memory cards. We all have a very bad habit of keeping them around, even after we stop using them. Here is the reality. Flash memory degrades over time. The Second Law of Thermodynamics states that entropy is always increasing. Entropy defines increasing disorder and randomness. It means that over time, stuff breaks down. The Third Law of Thermodynamics states that increasing entropy stops at absolute zero. But then, so has everything else, so in our day to day, most of use happily ignore the Third Law. Quad Level Cell flash memory is the least expensive type of flash memory and the type used most in memory cards. It has a mean time before failure in the range of thousands to tens of thousands of hours. MTBF is a statistical model that says half of the sample set will die within the MTBF time. Three years is 26,298 hours. And in the real world, that’s when we start to see an increase in the failure of memory cards. So if your memory card is three or more years in service, it is time to retire it and lay it to rest before you suffer a catastrophic data loss.

Card Bandwidth

All memory cards have a maximum bandwidth for data transfer. Makers express data transfer rates in Megabytes per second, contracted to Mb/s. This transfer rate is controlled by the memory controller built into the card. There are numerous different memory controller types in different cards. For SDXC type cards, the greatest defined transfer rate is UHS-III which can appear as the number 3 contained in a U. This is 30 Megabytes per second at minimum, but we find cards in this sector marked at up to 300 Megabytes per second. What is always missing is clarity. Is the 300 Mb/s sustained or burst, is it read, or write? This lack of detail should warn the buyer that missing information qualifies as misinformation, thus the card may never perform as advertised.

CF Express 1.0 maxes out at 1000 Mb/s or 1 Gb/s. CF Express 2.0 maxes out at 2000 Mb/s or 2 Gb/s. Again very pretty numbers but unless the card maker expresses sustained / burst and read / write pretty much meaningless foo foo dust.

Camera Bandwidth

Your camera’s internal memory bandwidth is nearly never documented. The closest that you will find might be in the manual in terms of the recommended card speed. The manuals never specify burst or sustained, but the metric for you to consider is ONLY sustained. The manual also never expresses read or write. The only one that actually matters is Write performance as Read is always faster than Write. Using a card whose performance is less than the camera bandwidth is wasteful and while a better performing card is the better long term buy, understand that your camera may not be able to take advantage of the card performance.

Buying Guidance

Buy the highest sustained write bandwidth card that you can find of the capacity that you want that you can afford. SDXC cards are now available with up to 2 TB capacity but honestly you will only fill that with long ProRes 4K video clips and if you are recording those on SDXC cards you are already losing, and if you are dumping 2 TB worth of stills on a single card, you have a much bigger problem between brain and shutter finger. Flash memory comes from different makers and also comes in different quality grades. Samsung is the largest manufacturer of flash memory in the world. Kioxa, formerly Toshiba, is the second biggest. Further down the list is the American company Micron and the Western Digital company that now owns SanDisk. You get what you pay for. You will find cards with great appearing specs from companies that you have never heard of who are offering cards at very low prices because they are buying the lowest grade of memory that they can, often the memory that Samsung or Kioxa would never use in their own products. I have often recommended SanDisk in the past, but with the recent catastrophic failures of multiple SanDisk SSDs, I am less inclined to do so. Micron used to build the Lexar brand but it was sold to another company some years ago. If you can find cards specifically from either Samsung or Kioxa (often labeled Toshiba), I would suggest those.

Card Readers

Most all cameras have the ability to be used as card readers connected via some flavour of USB to your computer. Understand that this method is your path of last resort. USB controllers used in most cameras are still of the ancient USB 2 variant, offering a maximum throughput of 480 megabits per second. Note that the metric is bits not bytes so this so called high speed USB actually maxes out at 60 Megabytes per second. For a 50 megapixel RAW that averages 80 megabytes in size, it means that 100 images will require at minimum over two minutes to transfer on a wholly dedicated USB bus. But USB is a shared bus that runs at the throughput of the lowest performance device on the bus, so figure a lot longer. USB 3 maxes out at 625 megabytes per second, but again only on a dedicated bus with a single sender and single receiver. Which your computer does not have as all USB busses are shared across multiple ports.

We have also become accustomed to multi card readers, that would allow you to dock all kinds of different formats into a single reader box. What is never documented is that these devices run at the throughput of the slowest interface in the unit. So if the device supports the ancient XD format, your SDXC transfer rate is going to be about the speed of a snail. This is why you do not find CF Express in multi format readers, the performance would be unusable. Even a combo SDXC / CF Express reader is going to be a lot slower than a dedicated CF Express reader. If your camera uses CF Express cards, get a USB 3.x reader that only uses CF Express cards, or you will be very sorry. I would say the same thing if your camera uses the highest performance SDXC cards as my Blackmagic Design 6K video camera can. I still won’t use those cards in that camera because the cards are just too damn slow for the media, but I hope that you get the point. Stay away from multi card readers. Yes you may have to plug and unplug different readers. Oh well.

For best card reader performance, plug your USB 3 card reader directly into a USB 3 port that is on its own USB 3 bus in the computer and ensure that nothing USB or USB 2 is on that bus. If you must use a USB 3 hub due to lack of ports, ensure that the hub goes direct into the computer and again into a USB 3 port that is not sharing the bus with anything running at USB or USB 2 rates. Keyboards, mice, webcams and USB sticks are all simple devices that can throttle your USB bus.

Thank you as always for reading. Please post comments or click the links to send in a question. If you shop at B&H Photo Video, please use the link on my site’s main page. it pays me a small commission and incurs no extra cost to you. Until next time, peace.