Re: Linux fs.aio-max-nr Leak?
- From: Kenny Payton <k3nnyp@xxxxxxxxx>
- To: alever22@xxxxxxxx
- Date: Mon, 29 Sep 2014 12:46:12 -0400
I'm not looking to start another flash debate but I will say we have found
it to be very reliable.
This particular problem is not limited to environments with flash storage
and I have observed the behavior across numerous environments for a number
of years. It certainly seems like a leak and the graphed trend shows the
same. The most recent occurrence was after 165 days of being up on a very
active database.
The fact that Oracle's pre-install rpm sets this to 1M leads me to believe
they are aware of the issue. 1M outstanding aio events seem a bit
excessive even for a busy database. If the requests were being managed
properly I would suspect we would see a significant drop off during off
hours but the trend is to vary slightly throughout the day but day to day
the trend line continues to climb.
I just came across this Pythian article where they did more digging than I
back in 2012. They claim Oracle support recommending setting aio-max-nr to
50M.
http://www.pythian.com/blog/troubleshooting-ora-27090-async-io-errors/
On Mon, Sep 29, 2014 at 12:09 PM, Alessandro Vercelli <alever22@xxxxxxxx>
wrote:
> Maybe the debate abount pros and cons of flash/SSD storage vs magnetic
> hard drives has been taken thousands of times without a winner, but I
> personally would use a non-magnetic disk only for os filesystems (and being
> compelled to use flash storage), first of all because of performance
> degradation.
> In the specific situation, I'm almost certain the problem is due to flash
> storage.
>
> Greetings,
> Alessandro
>
>
> ---- On Mon, 29 Sep 2014 16:50:46 +0200 Kenny Payton wrote ----
>
> >
> >These are pretty active databases. The instance in question for this
> event is 20T, all flash storage, in size and runs around 15k iops. Oracle
> Linux 6.3.
> >
> >
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
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