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What is the functional difference b/w NVRAM and Flash memory?

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  • What is the functional difference b/w NVRAM and Flash memory?

    I know Flash memory is used to store the images of the IOS and NVRAM is used to store the startup configuration file.
    I have google to know the functional difference between them.But, I didn't get the answer. Every one saying "Flash memory is used to store the images of the IOS and NVRAM is used to store the startup configuration file".

    I would like to know the functional differences between them so that I can understand why Cisco has used both of them.

    Thank you for your time.

  • #2
    Re: What is the functional difference b/w NVRAM and Flash memory?

    Good question. Funny how theres no clear answer and all the "experts" just copy and paste the same article to their websites.

    As a CCNA I couldn't tell you and I've looked for the answer many times. All I know is that NVRAM is fast, like RAM but when you cut power RAM goes blank, NVRAM doesn't so you won't lose your startup-config file.

    Well then why not just store the startup-config in Flash!? A possible answer could be that you can configure the boot register to ignore NVRAM.

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    • #3
      Re: What is the functional difference b/w NVRAM and Flash memory?

      I do not know what is the physical difference but one thing is sure, is a great solution having NVRAM, nice safe working memory; keeping IOS safe at Flash.

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      • #4
        Re: What is the functional difference b/w NVRAM and Flash memory?

        Originally posted by bspkumar View Post
        I know Flash memory is used to store the images of the IOS and NVRAM is used to store the startup configuration file.
        I have google to know the functional difference between them.But, I didn't get the answer. Every one saying "Flash memory is used to store the images of the IOS and NVRAM is used to store the startup configuration file".

        I would like to know the functional differences between them so that I can understand why Cisco has used both of them.

        Thank you for your time.
        Like you said "Flash memory is used to store the images of the IOS and NVRAM is used to store the startup configuration file"

        Traditionally, flash has a much larger capacity and for that reason can contain many different IOS versions, backups of IOS before upgrades, etc, the NVRAM is very tiny and super fast, it's useful to quickly boot the device, also to quickly save the run to start especially when the config is very large (hundreds of lines)

        Also an advantage of Flash is that it's mobile, you can take it out for backup purposes, etc.

        I don't think there's a concrete difference between them, they each have their practical uses but I don't think there's a difference performance wise.
        Last edited by toastman; 29th January 2010, 19:25.

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        • #5
          Re: What is the functional difference b/w NVRAM and Flash memory?

          So far this mystery is no clearer.

          toastman you contradicted yourself saying NVRAM is superfast fast then closing by saying they both offer the same performance...

          To make it more confusing, the ASA's don't have NVRAM, the config goes on the Flash. Our ASA runs at 1500+ lines with no delay in saving it. So I doubt that was the reason for NVRAM.

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          • #6
            Re: What is the functional difference b/w NVRAM and Flash memory?

            In my experience NVRAM is like cmos set up ram on a PC or apple computer. This is not really "non volatile" since when the cmos battery dies or is removed this memory looses its data.

            Flash memory, on the other, hand retains its data even when removed from battery or other source of power.

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