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Re: 100% CPU

From: Mladen Gogala <>
Date: Tue, 20 May 2003 05:21:54 -0800
Message-ID: <>

> Someone telling you that the cpu should be at zero percent is just being
> silly, however running at 100% is not an optimum condition.

Nope, it's not an optimum condition. It means that the company needs a bigger box. As for those zeros, it was a percent sign (%), not zeros.

> As one of the
> evil Sys Admins that you mentioned,

Oh, I wouldn't say evil creatures. Sys Admins are just vile, not evil. I know, because I used to be one myself.

> I personally prefer my servers to not go
> over 30% utilization on average, and prefer spikes to stay under 70%. If
> your hardware is running full bore all the time, two things will happen 1)
> Your hardware will wear out faster, especially hard drives, and 2) Your
> users will notice a slowed response time and complain.


> I'd say any server
> that runs over 50% usage on a regular basis is probably a good candidate for
> either an upgrade or some load balancing.

Probably true, but the black art of load balancing is mainly how to avoid IOs, put everything in memory and let CPU do the rest. If CPU is running at 100%, there isn't much point in classic load balancing, the only thing left is to look for a cheaper and more efficient algorithm.

> These figures can vary some with
> your budget and business needs but as a generic rule I think many people
> will agree with me in principle. Besides, if you're running at 100% during
> normal usage, what happens when a spike comes along like a shift change?
> Your server is going to lag, and users will be affected.

Not necessarily. If we're talking about a huge batch job that will run from 3-5 AM, nobody will be affected. That doesn't mean that 100% CPU is a good thing, it just means that you don't need to cancel the job or page your VP when that happens.  

Mladen Gogala
Oracle DBA
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Author: Mladen Gogala

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Received on Tue May 20 2003 - 08:21:54 CDT

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