Datalight News: Enhanced Power Fail-safe Handling of NAND Flash Errors
FlashFX Tera flash driver software with support for enhanced power fail-safe handling of read disturb errors and charge migration on NAND flash memory.
Datalight Inc., leading developer of flash file systems known for simplifying support for complex flash memory technologies, today announced the latest version of its market-leading FlashFX Tera flash driver software with support for enhanced power fail-safe handling of read disturb errors and charge migration on NAND flash memory.
Today read disturb and charge migration have increased in frequency such that read-only portions of the flash now need more careful attention. As systems have become more complicated with larger applications that use demand-paging, there is an increasing read rate. When coupled with the increasing susceptibility to read disturb errors due to shrinking lithography these storage demands have created a situation that must be mitigated if devices are to achieve their expected lifetimes.
“Our customers build products that are expected to last for years, sometimes decades,” said Kerri McConnell, VP of Sales and Marketing for Datalight. “Despite rigorous testing of their products prior to deployment, too many of them were experiencing shortened product lifetimes due to uncorrectable errors in the portions of their storage array without active management. Being able to address these proactively through a software update means reduced RMAs and happier end users.”
NAND flash memory can exhibit gradual loss of stored data due to the “read disturb effect” or to charge migration over time. The read disturb effect occurs because reading a page causes a weak programming voltage to be applied to all of the pages in the erase block, beyond just the one being read. Frequent reads in an erase block increase the likelihood that unprogrammed cells can become programmed. Charge migration, which can occur even if the flash is not accessed, causes programmed cells to be appear to be erased. This effect happens over a long period of time, but it may increase depending on operating or environmental conditions. These passive errors are now occurring more frequently because both read disturb and charge migration worsen with shrinking lithography, which is being driven by the need for higher and higher density.
Bit errors are expected in NAND flash, and error detection and correction (EDC) must be used. An error correcting code (ECC) is calculated and stored when a page is programmed. Later, when the page is read, the ECC can be used to detect and correct errors, up to some maximum number. If more bits are in error than the ECC can correct, the correct page contents are not recoverable. Without the active management of the entire flash array, these passive but correctable errors can build up undetected, and therefore uncorrected, until the device becomes unusable.
Prior versions of FlashFX Tera successfully mitigated read disturb and charge migration related errors in portions of the flash array managed by the software because the techniques of wear-leveling and compaction served a similar function. However, some applications store data using only the low level access routines, rather than higher level FlashFX Tera software functions for error management, because those areas need to be accessed by a small boot loader without sufficient space for sophisticated flash management software. This is typical, for example, with Microsoft Windows Embedded Compact and derivative operating systems that store a large system image in read-only partition. The new version of FlashFX Tera adds the features for safely and effectively handling read disturb and charge migration mitigation to these “unmanaged” portions of the flash array.
“The insidious nature of read disturb and charge migration can mean that a device will pass all of its testing with flying colors, only to fail without warning in the field,” said Glenn Sikkema, FlashFX Lead Developer for Datalight. “If the flash driver in the system is not recognizing and correcting read disturb errors and charge migration over the entire flash storage array, the product is at significant risk of premature failure.”
Other recent feature additions to FlashFX Tera include support for SPI (Serial Peripheral Interface) NOR. FlashFX Tera provides support for a wide range of NOR, SLC and MLC NAND, and sophisticated NAND controller technologies. Now system designers have access to the flexibility, wear leveling and other patented Datalight technologies on SPI NOR flash.
Often chosen by OEMs for its low pin count which simplifies hardware design for devices such as printers and ultra-thin computers, SPI NOR is complex from a software perspective and requires sophisticated drivers to ensure reliable data storage and fast access times. By using FlashFX Tera OEMs can get to market faster with a more robust solution.
In addition to broadening the flash memory technologies supported by the product, Datalight has also expanded the operating systems supported to include Linux version 3.12, Wind River VxWorks 6.9.3 and Microsoft Windows Embedded Compact 7.
FlashFX Tera version 3.1 is available immediately from Datalight and its worldwide network of resellers. Existing customers who have current Technical Support and Maintenance Agreements are eligible to receive this version for no additional fee by contacting Datalight.
Datalight, Inc. headquartered just north of Seattle, Wash., develops technologies to reliably manage critical data in embedded devices. Datalight file system and device driver software ensures reliability, performance and long product life and is used worldwide on many of today’s most well-known devices. For more information, visit www.datalight.com/ or call 800.221.6630.