Format of flash caused 100% cpu

[Josh Sprang]

I had an issue today on a 4507r today where when I formatted the compact flash in slot0: (512mb) it caused the CPU to spike to 100% this took about 1.5 hours and did not cause adjacency loss or any thing, but was worrisome. This was a sup IV is this normal and should u let it complete like I did? Also when I copied the os to it from boot flash it caused the same behavior. I have done this a bunch in 6500 sup 720 without this issue

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[Leo Laohoo]

Never seen this before.  What IOS version are you running?

If you don't regularly do anything to your CF then I'd ignore it.

[Josh Sprang]

12.2(54)sg fc3 advanced enterprise services.

This cf does not stay in this chassis. The CPU went to 100 when I copied the os from sup boot flash to slot 0.

I would just like to know about this one never had this prob before and I always thought this was safe to perform during the day.

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[Richard Burts]

I do not have lots of experience with formatting flash on a switch and so can not say whether this is normal or not. But I would assume that the activity of formatting flash is carried out entirely in the CPU and am not surprised that it would have caused high CPU (and am a bit surprised that it took 1.5 hours).

I will offer this observation: Josh has not told us how the switch is configured and so we do not know how much of its forwarding activity is done in hardware and not in the CPU. But I would assume that most of its forwarding activity was done in hardware and that the CPU is used for control plane activity. And in this case it is not dangerous that CPU was high because it would impact the forwarding capability of the switch.

HTH

Rick