This article entitled Advances in Nonvolatile Memory Interfaces Keep Pace with the Data Volume, recently published in RTC Magazine, gives a nice overview of maintaining performance on newer technologies.

Learn more about Datalight and ClearNAND

A recent article by Doug Wong compared performance characteristics of eMMC and ONFI specification EZ-NAND, specifically Toshiba’s SmartNAND here: http://www.eetimes.com/design/memory-design/4218886

One consideration I would add to this quite excellent summary is about the availability of drivers. Raw NAND has been around for quite a while and the market supplies a large range of drivers. Many of these will utilize the basic functionality of SmartNAND and other EZ NAND chips with only small modifications. Drivers for eMMC, on the other hand, are much harder to find. Only Linux has a freely available driver, which Google’s Android has taken advantage of in recent releases.

At Datalight, we continue to be excited by both of these new technologies. From the JEDEC eMMC parts, the cool features such as Secure Delete and Replay Protected Memory Block are very exciting. On the other hand, the sheer performance of Toshiba’s SmartNAND and other EZ NAND solutions is very much in demand.

To protect against unexpected power loss, so common in the embedded world, file writes need to be atomic.

Linux file systems ext3 and ext4 were designed for server or desktop environments. Google developer Tim Bray suggests that appropriate use of fsync() can mitigate the risk of data loss, but I am sure that’s not the best solution. The use of delayed allocation means that metadata is committed but the data is not. Alternatively, both can be committed to the journal at a performance penalty. Performance is crucial in both desktops and devices, but not at the expense of data corruption.

This problem is readily demonstrated when updating files, an action which usually happens “in place”. This is quite common in database and other important system files. When power is lost, data can be overwritten only partially, or else metadata can be altered to point to where the data will be updated but has not been. Another alternative to liberal use of fsync() is a rename strategy, that is, write only new data, then rename and replace the old file. Rename is atomic, at least.

The best solution, and one which does not require applications to change the way they do writes, is to perform all data writes atomically. In addition to that, the file system should never overwrite live data and always retain a “known good” state on the media. This way caching does not have to be removed – either user data changes get to the disk fully or not at all. No partial writes or incorrect metadata, and no mount-time journal rebuilds or disk checks either.

Instead of adapting a desktop or server file system for embedded use, it is far better to use a file system designed specifically for embedded use.

View whitepaper: Breakthrough Performance with Tree-based File Systems

Do you need defrag? It mostly depends on your hardware and your use case. While defragmenting a file system can make the computer run faster, it’s not the only answer.

Fragmentation is usually caused when modifying a file. Overwriting the file or making it larger means storing a fragment of the file in a new place, unless the file system creates a complete new copy of the file. Databases are particularly susceptible here – they are usually large files and often updated in the middle.

Another way fragmentation happens is when the file system initially stores the file in pieces. This could happen if the file system is not configured to keep file blocks together, or if the media is fairly full and there are no spaces of sufficient size for the new file.

What about the impact of fragmentation? In the days of rotating media, a fragmented file meant extra head movement and platter rotation to read the file. With flash media, the extra overhead is just additional block reads – a far smaller cost.

Avoiding fragmentation if you’re using Reliance Nitro can be as simple as customizing your transaction points. Instead of transacting on a timed basis, create a new transaction point only when the entire file is on the media, at “file close”. Similar settings may be available on other file systems.

If your use case causes fragmentation, a valid workaround might be to reformat the media after backing up the database files. A fresh file format is fairly quick on modern hardware, and can be coupled with a bad block test as well.

Read more about Reliance Nitro

Bothell, WA, – May 5, 2010 – Today Datalight announced support for Linux kernel versions up to 2.6.33, the most recently released Linux versions available. FlashFX Tera, the file-system independent flash memory manager and Reliance Nitro, the highly-reliable, high-performance file system offer much faster mount times than UBIFS, YAFFS, or JFFS2. In addition, the Datalight products boost write speed over the standard file systems and provide out-of-the-box support for over 300 different flash memory parts from all the leading suppliers. Linux is finding its way into more devices such as smart phones, automotive infotainment, and industrial equipment which require both responsiveness and 100% data reliability.

“With the growth in adoption of Linux for data-intensive embedded devices, OEMs need a flash file system that better supports their reliability and performance requirements.” said Roy Sherrill, Datalight CEO. “By supporting the most recent kernel versions of Linux we’re filling that gap in the market with a robust, commercial-grade solution backed by our reputation for responsive, high-quality support.”

FlashFX Tera supports the full range of flash technologies including NAND, NOR, and MLC NAND flash in a single driver. Its patented wear-leveling and bad block management extend the useful life of devices using flash. While FlashFX Tera can be used with virtually any file system, pairing it with Reliance Nitro provides an optimized data storage software stack to simplify system development.

FlashFX Tera 1.2 and Reliance Nitro 1.2 are available immediately from Datalight and the Datalight worldwide network of channel partners. Please visit us at http://www.datalight.com/partners/worldwide-sales-partners to find a reseller near you.

The Reliance family of file systems and FlashFX family of flash media managers comprise the Datalight flash file system solution. Reliance was designed from the ground up for high reliability applications. Dynamic Transaction Point™ technology gives developers full control over performance and data protection characteristics, protecting users from file system corruption, even after unexpected system interruption. Embedded applications can benefit from faster boot times that remain consistent for the life of the product, regardless of disk size. FlashFX™ Tera features pre-written support for over 300 flash parts, works with virtually any NAND controller, and features wear leveling, bad block management, and background compaction for unrivaled performance.

For information, contact:
Kerri McConnell, Director of Marketing
425.686.1069
kerri.mcconnell@datalight.com

Watch Rob Hart demonstrating the Datalight flash file system on the Beagle Board with Windows CE 6.0

With the release of our new file system this week, Reliance Nitro, we asked our Account Managers what they liked most about our new product. Their answers of course included reliability and high performance. Wes Johns and Phillip Allison were so excited they decided to make a video…  watch the youtube video

We’re totally psyched about Reliance Nitro, our newest file system (yes, we’re file geeks), and we’re always on the lookout for opportunities to show off the performance and reliability attributes it adds to Windows Mobile and Windows CE. When we discovered the relatively-new Beagle Board, it occurred to us that a small, low-cost platform might be just the thing to demonstrate Nitro’s amazing benefits. As you’ve probably heard, the Beagle is making waves with its low cost (around $150) and diminutive size. It uses an OMAP 3530 processor and 256MB of NAND. Though they are most commonly used with Linux, we lucked out in having a partner (MPC Data) who has already developed a Windows CE BSP for it. After a few phone calls, the wizards at MPC Data were able to develop a slick video playback demo app, and presto, the Reliance Nitro Beagle Demo was born! Amateur videographers that we are (ok, REALLY amateur), we recently videotaped John Burnham, who has been working on this project on the Datalight side (and who is a really good sport, btw) showing what happens when power is interrupted during a file write and the extra reliability factor of Reliance Nitro on Windows CE. Be sure to check it out here.

Sea Change Hits Consumer Electronics as Customers Demand Long-term Value

For the first time in more than a decade, people are saving again. In 2007 and years prior, the savings rate hovered around zero as we maxed our credit cards and lines of credit, driving the savings rate into the red and giving the world’s manufacturing base an almost unbelievable boom. In January 2009 though, something unexpected happened; the US savings rate suddenly moved above 5%, the highest in decades. As news of our cloudy economic picture has emerged, consumer behavior is shifting away from status-seeking luxury purchases toward more value-based buying patterns, forcing manufacturers around the world to take notice. And after decades of excess, the shift to thrift is looking like a lasting trend.

But what does this mean for Embedded? As consumers focus on needs over wants, they will increasingly seek out products that are proven durable and reliable.

This will have broad implications for manufacturers of everything from cars to clothing, refrigerators to embedded devices. Today’s consumers are choosing efficiency, durability and value over gee-whiz gadgetry. Consumer mobile OEMs too must focus on delivering value and fewer, more targeted features. Rather than packing devices full of a laundry list of apps and expensive hardware, this means streamlined offerings and more segmented products, while making sure the consumer doesn’t feel like they’re missing out. Motorola’s new EM330 is a prime example of this kind of pared-down, demographic-specific approach. The phone, called the MOTOROKR STAR is marketed specifically toward music lovers, offering a basic clamshell with music recognition software and download-on-the-go at a price point in the sub-$200 range.

As OEMs scramble to add value and enhance their reputations for durability and reliability, Datalight responds with products that support those goals. The combination of flexible flash management that lowers bill of material costs, wear-leveling algorithms extend flash life by several times, and the rock-solid reliability of our file system become essential components of a strategy to provide value to customers.

Many have remarked that markets are driven by a combination of fear and greed. Though the pendulum has recently taken a dramatic –and we believe temporary– move in the direction of fear, ultimately we know a move away from excess is good for all of us and good for the world we live in. Here’s hoping the trend toward value and quality is a long-lasting one.

5 Reasons for Ditching Managed NAND
Everyone knows that NAND has challenges: from factory bad blocks and spontaneous bit failures to endurance limits, etc. That’s why a few years ago managed NAND (NAND flash plus an integrated controller) seemed to be the answer, offering the density of raw NAND, while mitigating many of its inherent limitations. What many device manufacturers may not realize is that the management hardware comes with significant costs, both in terms of dollars per part as well as design limitations. In the world of tradeoffs in which every system designer lives, there are solid technical reasons to consider using raw NAND and leaving the management to software instead. While there are clear commercial advantages for Datalight (as a provider of vendor-neutral software-based flash management) to advocate this approach, we also believe that there are strong technical reasons that flash silicon vendors would do well to embed ECC capabilities into their NAND flash devices rather than relying on ‘total hardware’ solutions such as eMMC or other complex and costly controllers. Beyond the benefits outline below, this approach would allow the flash manufacturers the ability to continue to differentiate their products from others in the industry.

1.    Cost
The cost of managed NAND parts is coming down, but the stuff still sells at a premium over its raw NAND brethren. 

2.    Flash Optimization
There are many new features of NAND available to us today.  Performance features such as cached reads, multi-plane operations, concurrency, and others are becoming invaluable to keep performance at the ever-increasing demands of portable media. The Open NAND Flash Interface (ONFI) has defined a standard method to query the capabilities and characteristics of NAND flash which can be put to use by both software and hardware systems. A software media manager offers the flexibility to take advantage of the most current flash memory features and put them to use efficiently, or to avoid certain features that may be unproven or problematic. A software solution will allow a developer to take full advantage of the media’s characteristics and features unburdened by the indirection or inability for the hardware to expose them.

3.    Visibility/Flexibility
Software (in general) is easily inspected and validated. Features such as wear-leveling move data around the flash device to optimize its life expectancy. Without the ability to inspect source code, a managed NAND solution makes it difficult to validate wear-leveling operation and/or characterize its effect on performance and reliability.  Hardware implementations are often generalized to suit a majority of use cases, while a software solution is easily tailored to the specific use case during development.

4.    Performance
Speaking of use cases, there are many system features that are not available to hardware that may make a generalized hardware solution less advantageous to a specific use case.  For example, system idle time can be used to improve the media performance by scheduling background cache operations and compaction to occur then.  Coordination between the file system and flash media manager can further optimize operations by freeing space when it will no longer be needed and having the media manager code cache certain regions of the flash where meta data might be held. Migrating flash management features to hardware removes this ability to coordinate with other components of the software stack, such as file systems.

5.    Reliability
Lest you think we believe that everything is better left to software, consider error detection and correction (EDC). Error rates are increasing substantially as flash manufacturers push the limits of physics.  Errors can be introduced externally by heat or other radiation, during writes or reads of data, and even to data that was successfully written at a different time. Historically SLC NAND flash required only a single bit error detection and correction (a hamming code is usually sufficient), while MLC parts require minimally four bit EDC.  As the die sizes continue to shrink, error rates will continue to increase, even for SLC flash. 
Calculating the codes to detect and correct such errors is getting increasingly complex and solving such a solution in software for higher-bit EDCs (above 4-bit) is time consuming and often unacceptably slow.  Hardware ECC is a necessary requirement for systems with high EDC requirements and where performance is a concern.

Many of the processors on the market today are incorporating EDC in their NAND controllers. Choosing one of these processors (e.g. TI OMAP 35xx) in combination with raw NAND flash and software management can give you the high-performance EDC to handle next generation flash while maintaining the design flexibility that a software manager provides.

Flash manufacturers have much to gain by adding ECC code into their NAND flash parts.  They know better than anyone what kind of ECC is necessary for a specific part and by adding just that one piece of hardware to their offerings, rather than the jack of all trades, master of none approach of complete flash management, they will better serve the markets. 

In short, features should reside where they can be handled most efficiently; ECCs belong in hardware, other flash management functions belong in software.  While managed NAND certainly has its place and its appeal in the market, we believe the best combination of value, performance and flexibility lies in using a combination of raw NAND and hardware with built-in ECC capabilities.