Extracting IOS image on 3560/3750 take 20min and causes high cpu load

Unanswered Question
Aug 12th, 2010


I used the "archive download-sw" command on several Catalyst 3560 and 3750 (via ssh session) to copy new ios images to their flashes and extract them.

While the extracting took nearly 20 minutes I experienced 100% cpu load on the switches, a "show proc cpu" in a second - very slow - ssh session displayed the ssh process with 99,x%.

Does anybody know if this is normal behaviour and if extracting an image this way is affecting the switching/routing performance of the switches?

Many thanks in advance,


I have this problem too.
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Richard Burts Thu, 08/12/2010 - 07:52


I am not sure if the high CPU during extract is typical, but suspect that it is.

Since most of the forwarding in the switches is done in hardware, the fact that CPU is busy should not impact performance of the switch.



Jayakrishna Mada Thu, 08/12/2010 - 10:33

Hi  Thorsten,

The CPU utilization will spike when the CPU access the flash file system. Accessing the flash is a CPU intensive operation.

Spikes of usage during flash file access is known behavior. Hence you will see CPU spike during image upgrade.

It will not affect the traffic flowing through the switch but might affect other protocols on the switch like routing.

There was a bug opened on this issue but it was closed as it was expected behavior so the only suggestion is to upgrade duing a maintenance window.


Hope this helps.


Leo Laohoo Thu, 08/12/2010 - 15:46

I used the "archive download-sw" command on several Catalyst 3560 and 3750

If you use the command "archive download-sw", expect the CPU to go through the roof but this alone WILL NOT cause the switch to crash or fail.  Data traffic is still maintained.

This is because the "download-sw" switch, correct me if I'm wrong here, is loaded onto the appliance's memory before it is being extracted into the flash.


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