Researchers at IBM Research center have demonstrated a reliable data storage medium which can overtake SSD and disk drives markets within no time. The scientists have demonstrated reliable storage of three bits of data per cell using a relatively new memory technology know as Phase Change Memory, being developed from past two years.
Phase Change Memory of IBM has attracted a lot of storage industry’s attention as it is a universal memory technology based on its combination of R/W speed, endurance, non volatility and density. For example, PCM doesn’t lose data when powered off, unlike DRAM, and the technology can endure at least 10 million write cycles, compared to an average flash which tops just with 3K write cycles.
When it comes to application of Phase Change Memory, entire databases could be stored in PCM for blazing fast query processing for time critical online applications, such as financial transactions. Machine learning algorithms using data sets will also see a speed boots by reducing the latency overhead when reading the data between iterations.
Methodologically speaking, Phase Change Memory looks like a promising alternative to standard NAND memory used in solid state drives. It uses Chalcogenide- chemical compound containing one or more Chalcogen Anion and at least one more electro positive elemental alloy in two physical states- crystalline and amorphous.
Since, the resistance of the alloy in two states is different; this property can be used to store binary information 0s and 1s. The physical state can be switched by applying heat, and as both states are stable they persist until they are actively changed. State changes can be performed on a cell (and therefore data written) about a million times, which compares favorably with the typical 30,000 write cycles offered by high-end SLC NAND cells found in enterprise class SSDs.
The problem with PCM is that it has high write latency, but computing giant IBM has demonstrated that a hybrid device that uses PCM, NAND and DRAM on a single controller can work up to 275 times faster than a standard SSD device. This arrangement offers read times between 100 and 300 nanoseconds, and write times of between 10 and 150 microseconds.
In order to achieve multi bit storage- the researchers at IBM have developed two innovative enabling technologies- a set of drift immune cell state metrics and drift tolerant coding and detections schemes.
These schemes adaptively modify the level thresholds that are used to detect the cell’s stored data so that they follow variations due to temperature change. As a result, the cell state can be read reliably over long time periods after the memory is programmed, thus offering non-volatility.