Re: Sudden drop in DBb performance

On 09/05/2011 01:45 PM, Scott Marlowe wrote:
> On Mon, Sep 5, 2011 at 8:08 AM, Gerhard Wohlgenannt<wohlg@ai.wu.ac.at>  wrote:
>> Below please find the results of vmstat 2 over some periode of time .. with
>> normal database / system load.
>>
2  1 1344204 240924 104156 31462484  350    0  1906   234 3687 4512 12  3 77  9
>
> Your IO Wait is actually pretty high.  On an 8 core machine, 12.5%
> means one core is doing nothing but waiting for IO.
>

My server is 2-core, so these numbers looked fine by me.  I need to remember core count when I look at these.

So the line above, for 2 core's would not worry me a bit, but on 8 cores, it pretty much means one core was pegged
(with9% wait?  Or is it one core was pegged, and another was 72% io wait?) 

I have always loved the vmstat output, but its starting to get confusing when you have to take core's into account.
(Andmy math was never strong in the first place :-) ) 

Good catch, thanks Scott.

-Andy