SSD Controllers

Baidu Goes Beyond SSDs

Baidu's SDF: Software-Defined FlashI have to admit that it’s embarrassing when The SSD Guy misses something important in the world of flash storage, but I only recently learned of a paper that Baidu, China’s leading search engine, presented at the ASPLOS conference a year ago.  The paper details how Baidu changed the way they use flash to gain significant benefits over their original SSD-based systems.

After having deployed 300,000 standard SSDs over the preceding seven years, Baidu engineers looked for ways to achieve higher performance and more efficient use of the flash they were buying.  Their approach was to strip the SSD of all functions that could be better performed by the host server, and to reconfigure the application software and operating system to make the best of flash’s idiosyncrasies.

You can only  do this if you have control of both the system hardware and software.

The result was SDF, or “Software-Defined Flash”, a card that Continue reading

What’s In My SSD? SLC, MLC, or TLC?

SLC, MLC, or TLC?Someone recently asked The SSD Guy if there is a way to determine whether an SSD is SLC, MLC, eMLC or TLC.

I found it a little odd to be asked this, since most vendors tell what kind of flash they use in an SSD’s specifications, especially if it’s SLC.

Not finding it there then the next thing I would look at is the price.  Raw SLC NAND flash now sells for about 6-10 times as much as its MLC counterpart, so an SSD with a price of around $1/GB is likely to be MLC and one that sells for around $10/GB is probably SLC.

TLC SSDs are really rare.  There is the Continue reading

Comparing Samsung’s Planar and V-NAND SSDs

Samsung 3D V-NAND Press PhotoSamsung recently introduced  its 3D V-NAND-based 850 SSD which, according to The Tech Report, uses the same MEX controller as the company’s 3-bit planar SSD, the 840, introduced last year.

Samsung said in its keynote speech at the 2013 Flash Memory Summit that V-NAND consumes an average of 27% less power and runs at least 20% faster than its planar counterpart in an SSD application, all while providing ten times the endurance.  It’s only natural to assume that this would allow designers to produce a V-NAND SSD that would significantly outperform its planar NAND counterpart.

The SSD Guy had an opportunity to review Continue reading

LSI SandForce SSD Controllers Move the Knee in the Curve

LSI SandForce SF3700 Controller DuraWrite ImprovementsLSI’s SandForce has just rolled out its SF3700 family of four SSD controllers aimed at the Entry Client, Mainstream Client, Value Enterprise, and Enterprise Storage marketplaces. Performance is impressive, with worst-case random PCIe IOPS at 150K read/81K write and 94K/46K for the SATA interface.

The SF3700 family builds on the division’s first two product families by adding a choice of PCIe or SATA interfaces, LDPC error correction, and a boosted set of flash management features.  The SSD Guy will explore this last point after highlighting the other two.

By providing both PCIe and SATA interfaces LSI is directly addressing the future: PCs are aiming to move to the m.2 SSD specification rather than Continue reading

A New Way to Use SSDs

Micron's View of Computing - Speaker is the CPU, Audience is StorageIn his Flash Memory Summit keynote on Wednesday, Micron VP and Chief Memory Systems Architect Ed Doller made a compelling demonstration of the power and performance advantages of a new approach to computing.

With true showmanship, Doller had his co-workers hand out buttons with LED lights to the entire audience.  The LEDs in these buttons were either green or blue, with the colors randomly dispersed among the crowd.  Doller asked the entire audience to turn on their lights, then called one row of the audience to file up to the stage so he could determine whether each person’s button was blue or green.

He pointed out that this was like having a single CPU check the contents of a drive.  He then asked why things should work this way – wouldn’t it be more sensible to Continue reading

Extreme SSD Error Correction

Chuo University EmblemAt last week’s International Solid State Circuits Conference (ISSCC) Shuhei Tanakamaru, a researcher from Japan’s Chuo University, detailed a scheme to reduce MLC SSD bit error rates (BER) by 32 times over conventional techniques.  The approach used an impressive combination of mirroring, vertical and horizontal error correction, and a deep understanding of the most likely kinds of bit errors flash will experience.

This is a very novel and well-conceived technique that may find industry adoption in future SSDs.

The steps included in the paper are used in addition to the Continue reading

New Booklet: How Controllers Maximize SSD Life

SNIA SSD Controller BookSNIA (The Storage Networking Industry Association) has conferred a great honor upon the SSD Guy by bringing all of the blog posts in the series How Controllers Maximize SSD Life into a single printed volume of the same name.

Readers can either ask for a print copy from SNIA, or can download a pdf rendition by visiting the SNIA SSSI (Solid State Storage Initiative) education web page.

The NAND Band!

NAND Band Backstage PassDuring this month’s Storage Visions conference, SMART Storage Systems hosted a “NAND Band” party.  The company kept the details secret until the guests were all there, after which two “Blues Brothers” impersonators (SMART’s president John Scaramuzzo and Rick Neff, Director of Business Development) showed up in a video singing their new rendition of the 1966 Spencer Davis Group hit: “Gimme Some Lovin’.”   SMART’s version was called: “Gimme Some Endurance” and the lyrics centered around the importance of endurance in SSDs.

(SMART’s NAND Band should not be confused with the techno band named NAND which I only discovered while writing this post.)

The reception was held only a couple of hours after Continue reading

SSDs that Don’t Wear Out

The End of NAND Flash Wear?This is a bad day for The SSD Guy.  I just finished publishing an eight-part series explaining How Controllers Maximize SSD Life, then my evil twin The Memory Guy today published a post telling of a new flash design from Macronix that might just eliminate the flash wear-out mechanism!

But my concerns are inconsequential compared to the feelings of all those folks who have devoted phenomenal time and energy to develop wear management algorithms.

This all stems from an article in the IEEE Spectrum that details a flash chip design that Continue reading

How Controllers Maximize SSD Life – Internal NAND Management

Tempus FugitGiven that you have used all those other forms of improving SSD wear that we have discussed so far, but you still don’t find that this is enough, what do you do next?  Well a few SSD controllers go one step further and manage some of the inner workings of the NAND flash chip itself.

If that sounds like a significant undertaking to you, then you clearly understand why so very few controllers take this approach.  The information used to perform this function is not generally available – it takes a special relationship with the NAND flash supplier – and you can’t develop this relationship unless the NAND supplier Continue reading