What Went Wrong With TLC NAND

When Samsung pushed the envelope and introduced their TLC-NAND flash memory for general use, it had the makings of a landmark innovation. TLC (triple-level cell) NAND is cheaper to manufacture than either SLC or MLC NAND, as it works by fitting more data  into the same NAND cell—three bits per cell, rather than the one bit or two bits that single level (SLC) and multi-level (MLC) NAND can put away in one cell space.  You’d think TLC NAND would take over the market in short order; no reason to waste resources manufacturing more expensive SLC or MLC NAND.

When introduced the new TLC-NAND solid state drives seemed to have conquered all previous difficulties of TLC NAND with some state of the art firmware. Read speeds looked pretty; Samsung SSD 840’s 500MB/s is nothing to sneeze at and reliability was a non-issue.

But, mounting excitement over the potentially cost-effective storage innovation waned as performance problems were discovered.

In fact, it wasn’t long before users began reporting a new and extremely debilitating challenge. Those pretty read-speeds, that near 100% reliability: those only counted for new, freshly written data. Data that had been sitting on the drive for, say, all of eight weeks, would have deteriorated to a level that it could only be read at much slower speeds.

Meaning, by the time you had data sitting static on your drive for six months or a year, those previously high read-speeds would have been reduced to processing at a snail’s pace.

It turns out that this is a problem inherent in the TLC system. Although there’s a voltage drift that happens in every NAND drive over time, in SLC and MLC NAND, this drift is small, consistent, and can be accounted for in the reading algorithms. When you lock three data bits in a cell, though, data deterioration speeds up immensely. What’s worse, there’s no longer a generalized algorithm that can take all the shifting into account, so the old data is simply blurred.

Samsung has introduced two firmware updates in an attempt to smooth over the problem. The first, a fancy algorithm that was meant to take account of the voltage drift and factor it in where necessary, completely failed at solving the issue.

The second, while more successful, offers a somewhat unpleasant workaround: The drive is set to rewrite all data regularly, so nothing ever is old.  It does manage to get around the problem: if all data is new data, it will all be readable and quickly accessible. However, since every NAND SSD has a finite number of writes or rewrites, this isn’t an ideal fix.

What does this all boil down to?
Simply that TLC NAND is not the future of data storage, and it doesn’t even have a good seating in the present. If your data matters in the long term, you’ll want to go with a higher-quality NAND: MLC-NAND for your basic SSD needs, or SLC-NAND for industrial use or super-sensitive data storage. There’s no other way about it.

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Your microSD Card: Is Cost All That Matters?

They look the same and have the same capacity.  For consumers shopping for a microSD card, the only difference might appear to be their price. Does it really matter which microSD card you buy? Should you go with the cheapest option?

Turns out, there’s more to that little plastic chip than you can see on the outside.
It may come as a surprise, but choosing a microSD card is actually an important decision that affects the performance of your phone or other mobile device. Pair a cheapo microSD with your top notch smartphone and you’re setting yourself up for a whole range of problems, ranging from memory failures and corrupted files to crashing your entire phone OS.

“The fact that there are a lot of fake cards out there,” reports Richard Lai of Engadget interviewing Hugo Barra, Xiaomi’s Vice President of International.

The market abounds with SanDisk that is not really SanDisk, Kingston that is not really Kingston, and other major manufacturers that are possibly just cheap Chinese fakes. It’s not hard to print out a name-brand sticker and put it on a generic microSD. Barra elaborated on the problem:

“You think you’re buying like a Kingston or a SanDisk but you’re actually not, and they’re extremely poor quality, they’re slow, they sometimes just stop working, and it gives people huge number of issues, apps crashing all the time, users losing data, a lot of basically complaints and customer frustration. It’s gonna be a while before you finally accept that maybe the reason why it’s not performing is because you put in an SD card.”

Because of the prevalence of sub-quality microSD cards on the market, the problem has many smartphone manufacturers choosing not to put microSD slots in their high-end, flagship phones at all. There’s just too much potential for disaster and the problems that come up usually get blamed on the innocent phone, rather than the tiny memory card hiding inside of it, jamming up the works.

But despite the concern from big brands, microSD slots are still a big selling point for shoppers.
If you do value the ability to increase your smartphone’s memory beyond its out-of-the-box capacity, make sure the card you’re slipping inside is a quality product – not a phone-debilitating enemy in disguise.

It’s important to not only choose a brand you can trust, but also with a reliable distributor; preferably, an official partner of a top-quality brand like Panasonic or Kingston. Our official partnership with Panasonic is just one reason DIGISTOR is a preferred retailer for high-end, quality microSD cards you can trust. If you’d like to learn more about our quality control and microSD card compatibility, call up one of our sales associates for more information.

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