VAR-SOM-OM35/7/AM35 Linux Nand Flash Based FS

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1 Nand Flash based File-Systems – Usage guidelines

Follow the below guideline to ensure a reliable long-life file-system.

1.1 Nand flash and file-systems

Variscite uses SLC (Single-Level-Cell) NAND flash in its System-On-Modules, which is the preferred NAND flash technology in aspects of reliability. However, there is a limitation that flash memory has a finite number of erase-write cycles. SLC flash products are guaranteed to withstand around 100,000 write-erase-cycles (per block), before the wear begins to deteriorate the integrity of the storage.

Every change (of even 1-bit in a file), will cause a re-write of the whole file to the flash, causing a number of blocks to be re-written.

NAND devices also require bad block management by the device driver software, or by a separate controller chip. Windows CE / Linux have wear-leveling algorithms to ensure data integrity even in the case of a bad block appearing (Normal) in the Nand flash.

However, to ensure a long-life reliable file system, Where possible, try and keep the number of write cycles to the minimum!

  1. Keep on-going updating files (log files, data-bases…etc) managed at a RAM-based Folder (MyDocuments for example).
  2. Backup these updated files to the flash ( “Flash storage” or “mounted volume”, depending on platform) every certain amount of time. The longer the better.