How many times is ok to write in NVRAM?

Discussion in 'Tomato Firmware' started by landa, Mar 6, 2009.

  1. landa

    landa LI Guru Member

    Is there any possibility to damage your router if you write the firmware several times? About how many times is ok to write in NVRAM? Is there a limit?

    I flashed the router about 20 times, is too much?
  2. kenyloveg

    kenyloveg LI Guru Member

    Not really, MLC NAND can be flashed at 10000 times. And most could be 5000.
  3. landa

    landa LI Guru Member

    Everyone says that's not good to write frequently in NVRAM. No longer understand anything, you say can be written as 10000 times!
  4. mstombs

    mstombs Network Guru Member

    The limit's more like 400,000 times. Not a big concern for firmware flashing but the nvram area is an issue. Flash is written in blocks at least 64kB at a time, flash file systems have wear levelling algorithms to ensure all bits are equally cycled. The nvram data storage area is fixed location and same area written every time a "nvram commit" is done. Write a script to do this every second and it wouldn't be expected to last a week!
  5. landa

    landa LI Guru Member

    So, is no problem to flash/try different firmwares many times!!!

    Super!!! :thumbup:

    Thank's for the answers!
  6. szfong

    szfong Network Guru Member

    I had a La F*nera router that uses RedBoot, and the NVRAM area where the config file is located, which is written to each time you save, caused unexplained crashes. After writing a pattern of binary data and reading it back, I was able to relocate it from using that area. It was only written to perhaps 2 hundred times at the most. Routers tend to write to the same area over and over, and the quality of NVRAM chips they use are the rejects from flash drive manufacturers or their sources, since most router users don't constantly write to it like a flash drive. No form of spreading write cycles is used. I've got an Airlink101 router that also suffered NVRAM failure. These used dd-wrt for the Atheros, and dd-wrt puts ALOT of stress on NVRAM, writing to it even w/o user intervention, eg. bandwidth data. These were cheap $10 dollar routers though...
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