Re: Disk Device Busy (%) - What exactly is this?

Hi,
I have always considered the iostat/sar -d busy metrics important. When I saw your question I searched google again and I found this *old* document
that seems useful:

sunsite.uakom.sk/sunworldonline/swol-08-1999/swol-08-perf.html

Hope this helps
Dimitre

On 21/11/2011 16:45, Guillermo Alan Bort wrote:
> hi guys,
> recently we got an alert from OEM on the metric Disk Device Busy (%) (it
> was at about 99% or something like that).
>
> My Oracle Forums and Metalink search yielded some interesting results
> that say it's a false alert (what a shock!)
>
> So, the Documentation points to space utilization:
> http://download-east.oracle.com/docs/cd/B16240_01/doc/em.102/b16230/host.htm#BHAFEBDG
>
> Metalink corrects this as a documentation bug (another shock!)
>
> The description of the metric in the documentation leads us to believe that
> the metric checks the disk capacity. But this is incorrect and we have a
> documentation bug
>
> Bug.5099684 : EXPLANATION OF DISK DEVICE BUSY METRIC IS WRONG:
>
> In reality, this metric checks how 'busy" the disk is.
>
>
> So... what on earth does "busy" mean? Is it some sort of metric of how much
> I/O is being done on the disk? if so... how can this be a percentage?
> What's 100%?
>
> I don't much care for the alert as I'm pretty sure that it's either a false
> alert or something I can't do anything about in the short run... but I
> would like to know what I'm seeing so I can find a way to prevent it from
> happening again.
>
> Oh, the databases are on SAN with one of those cool raid 5 stripped across
> 50 disks or something. So I get LUNs, not physical disks. Does this mean a
> particular LUN is busy?
>
> Thanks
> Alan.-
>
>
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>
>

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