Methods Of Achieving Nonvolatility In Solid State Disks

Abstract

Solid state disks are coming into wide use in a variety of applications, where they replace rotating disks to achieve dramatic improvements in speed and MTBF; especially in severe environments. While rotating disks are inherently nonvolatile, solid state disks implemented with DRAM or SRAM devices are inherently volatile. Retention of stored data under power-down conditions is commonly required and is often mission critical. To meet this requirement, a number of backup methods have been utilized to provide varying degrees of nonvolatility. These include: dumping to the host system, batteries, UPS, backup to disk and tape media, and hierarchal memory systems allowing loss of the stored data in the solid state disk. More recently, inherently nonvolatile semiconductor devices are being applied to eliminate backing stores or the need for energy