Flash NAND media – an introduction

In Blog, Information by Administrator

Solid state disks and memory sticks.

Flash NAND based media is a non-volatile storage device. Flash-based storage media is found in camera memory cards, USB pen drives, camcorders, mobile phones, dictaphones, tablets like the iPad, and solid-state hard disk drives.

As the cost per gigabyte decreases they are becoming increasingly popular as storage devices where hard disk drives would be used. The most significant difference between flash NAND technology and hard disk technology is that the former does not have any mechanical components.

Here we have two images of flash-based media with their outer packaging removed:

USB pen drive components

1 USB Standard, Male A-plug
2 USB mass storage controller device
3 Test point
4 Flash memory chip
5 Crystal oscillator
6 LED (Optional)
7 Write-protect switch (Optional)
8 Space for second flash memory chip

Processor / controller chip failure

The SSD and memory sticks that CDR – Manchester Data Recovery Services – receives in for recovery usually relate to a failure of the controller chip. This is the component that allows the storage device to interact with the computer and control the way data is distributed through the flash nand chips. The controller converts requests for logical sectors (LBA values) into the physical locations on the actual flash memory chips. It also contains a wear levelling algorithm which extends the working lifetime of the device.

SSD PCB componentsWhen a controller chip fails one of the most challenging aspects is calculating where data is spread through the flash chip. Data is not recorded in a simple linear fashion. The controller chip is designed to increase the performance which means spreading data through multiple locations to allow, rather than having required data in sequential blocks. As such recovery of data from these devices can be extremely challenging.

For further reading please see this thorough introduction to Flash NAND media.