Every so often, the IT world gets news of a "breakthrough" in new storage media research, and this week it was IBM's turn to announce one in relation to a possible long-term replacement for NAND flash solid-state disks.
Big Blue on June 30 revealed that its Zurich-based PCM (phase-change memory) research unit has produced 90-nanometer-size chips that can store multiple bits of data per cell over time without the data becoming corrupted. This is a problem that has been nagging development since IBM started this project nearly 10 years ago.
Previously, each PCM cell was able to hold a single data bit, and even those became lost or corrupt at unpredictable times. IBM said this latest development can lead to solid-state chips that can store as much data as NAND flash disks (which now are up to 1TB in capacity) but feature about 100 times the data movement speed, to go with a much longer life span.
NAND flash is inherently slowed down by so-called erase-write cycle limitations. This is because NAND flash requires that data first be marked for deletion before new data is written to the disk, which slows the process considerably. PCM does not require erase-write cycles.
Thus, the extra erase-write activity causes NAND flash performance to degrade faster and, over time, wear out the disk. Typically, NAND flash disk life spans range from 5,000 to 10,000 write cycles in consumer disks and up to 100,000 cycles in enterprise-class disks.
In contrast, PCM can handle up to an estimated 5 million write cycles, IBM and Intel (through its PCM-dedicated Numonyx arm) both contend.