Flash Storage Solutions for Embedded Designs
High Reliability Flash SSDs, Cards and Modules for Industrial Applications
Posted by Biraj Jamalayam on Wednesday, 04 Jun 2014
Frequently we receive customer inquiries about our Industrial Storage products where they don't understand the difference between an Industrial and Consumer solution and how the technology and product quality differs.
While my colleague addressed this question from the point of view of product manufacturing, I would like to address it from the point of view of technology and specifically about the Industrial Flash Controller that transparently manages the host system interface to NAND Flash media.
As part of the NAND Flash management algorithm, Flash controller performs the following discrete tasks:
1) Error Check and Correction - Checking and Correcting any "flipped" bits mainly due to NAND Flash manufacturing defects or over use.
2) Garbage Collection - Optimizing the usage of the Flash media to achieve higher performance and reduce media wear.
3) Block Management - Allocating memory blocks into system and user space for efficient usage by the SSD.
4) Wear Leveling - Moving data between different physical memory locations to extend the SSD reliability and usage.
The specific capabilities of the Flash controller to perform the listed tasks is most important when selecting the proper storage device. But finding the appropriate technical information in the product description can oftentimes be quite challenging.
ECC coverage of the Flash Memory Controller are often specified directly in the features section of the Storage Device data sheet. While as the general rule, the greater the ECC capability the better, it should also be considered jointly with the NAND Flash component used in the drive. NAND Flash manufactured of the more advanced process technology node requires much greater ECC correction, while a NAND component manufactured on a less advanced process node has lower ECC requirements. Most Industrial Grade Flash controllers use BCH ECC algorithm capable of correcting from 24 up to 80+ single bit errors per programming page of NAND Flash.
The Garbage Collection, Block Management and Wear Leveling capabilities of the Flash Controller are not that easily defined in a data sheet. However one should be able to ask the Flash Card or SSD vendor about the life expectancy of the product. As part of the life time calculation the vendor determines the Write Amplification factor, which is the aggregate constant of the combined Garbage Collection, Block Management and Wear Leveling technologies of Flash controller.