IOS -- Why recommended Flash is Much more than Image Size

Unanswered Question
Nov 19th, 2008

Its Generally Observed that when we download an image the Image size is Much less than the Recommended Flash Card Size.


First Image Information CURRENT

Image Name s72033-pk9sv-mz.122-18.SXD4.bin

DRAM / Min Flash 512 / 64

Size ~~ 48 Mb

Second Image Information

Image Name s72033-adventerprisek9_wan-mz.122-33.SXH3a.bin

DRAM / Min Flash 512 / 512

Size~~ 78Mb

Why So ? Bcuz other files like config / vlan.dat dont demand Much space & For a Backup Image256 Mb would be Enough. Please Elaborate Your Answer

I have this problem too.
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Mark Yeates Wed, 11/19/2008 - 19:02


Generally memory sizes are incremental ie 16,32,64,128 etc... So of course you have to have the available amount of memory to be able to store the IOS on it. Many routers now come with the SDM GUI that takes up 6-8Mb on flash memory, and I think Cisco does take things like that into consideration.

On your second image with the 512Mb recommended amount of flash I think is a typo. I see no reason why 512Mb is required for a 78Mb file. You could hold several IOS files with that amount of flash (which is nice) but not required.

I believe that the vlan.dat and the startup-config are still housed in NVRAM. Which is a completely different file system than flash.




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