Patent For Flash File System

With flash memory becoming more widely used in different ways, preserving data integrity will become more of an issue. Flash memory is considered stable, but everything from rough treatment of mobile devices to the manufacturing process could increase the potential for data corruption.

At the same time, flash is using the same read/write file system as hard drives, which can be corrupted, particularly if there is an interruption during the read/write process.

Enter Datalight. The company has developed a performance and integrity enhancing technology called Datalight Reliance which was awarded a patent from the U.S. Patent and Trademark office this week.

Reliance eliminates data corruption by changing the way data is stored on flash memory devices, reduces I/O and speeds up performance all at once. It does this by dispensing with the File Allocation Table (FAT)-based file system normally used on flash devices in favor of its own.

“FAT was designed in the late 1970s for simplicity only,” Roy Sherrill, president and founder of Datalight told “It was not designed for mobility or reliability or being robust.”

Instead, Reliance uses what Datalight calls Dynamic Transaction Point technology to give complete control over how and when transactions are performed. Data is written in an all or nothing transaction using a variety of write methods more akin to a journaling file system.

This is needed because flash is being used in more areas, particularly in mobile systems, where it gets jostled and bumped a great deal. Along with the weaknesses of FAT, Sherrill said flash itself is becoming unstable due to the manufacturing process.

Flash has seen a 125-times increase in densities in the last seven years while making things smaller and cheaper, making things more fragile. “As the demand for more flash at cheaper prices continues, we will find that flash vendors do deliver the flash but it will be more susceptible to errors,” said Sherrill.

Part of that is due to the increase in flash cell density. For the longest time, there was a single level cell, or one bit per cell. Now it has gone to two bits per cell, and by 2009, it will go to three or four bits, all in a bid to make it more dense.

This causes bad blocks, just as hard drives get bad sectors. As the number of bits per cell go up and lithography goes down, the level of bad blocks that will occur will increase. “The issue is not how many bad blocks you get, it’s can you correct them and decrease the likelihood of more and fix the errors,” said Sherrill.

The Dynamic Transaction Point file system reduces the amount of writing to the flash memory, thus reducing wear on the cells that cause bad blocks. Sherrill estimates a 40 percent reduction in I/O and a subsequent improvement in performance as a result.

Datalight Reliance is sold to OEMs and mobile consumer product manufacturers for use in their cell phones, flash drives and other flash-based products.

News Around the Web