Disk Device Busy (%) - What exactly is this?
- From: Guillermo Alan Bort <cicciuxdba@xxxxxxxxx>
- To: oracle-l-freelists <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 21 Nov 2011 12:45:18 -0300
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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