Re: DBWR performance

From: Noons <>
Date: Wed, 16 May 2012 20:53:48 +1000
Message-ID: <jp00vs$frm$>

Mladen Gogala wrote,on my timestamp of 15/05/2012 10:35 PM:

> high I/O rates is not very good. If you want a Unix box that will handle
> high I/O rates well, buy AIX.

I fully concur: our P6 Aix box is astounding in its I/O capacity. Particularly with the combo Aix 7.1 and Oracle, I'm seeing some stunning improvements in I/O throughput.

> The main problem with Linux AIO is excessive polling, which wastes CPU.
> Linux creators are aware of the fact, so they have created two Linux
> specific API's to alleviate the problem: epoll and io_submit. Oracle is
> using io_submit but it doesn't seem to address the problem completely.

Didn't Oracle at some stage do something fancy with their own flavour of Linux?

> Oracle implementation of asynchronous I/O: instead of lightweight kernel
> threads, there are Oracle processes. If Linux version doesn't work well,
> try with Oracle's.

Makes sense.

 > Problem with Linux is, among other things, in the PC
> architecture which doesn't have a standard implementation of smart I/O
> channels. Mentioning the old ESCON channels would probably be rightfully
> considered rude in the Linux world. There is an I2O story, which is now
> defunct, but there is still no channel architecture on PC hardware, which
> makes PC I/O a lot slower than the I/O of the true minicomputer, like the
> ones offered by IBM or HP.

Yeah. And the backplane on the iPower series also has some accountability in all that. I am continually surprised at how much processing throughput our DW is pulling. Received on Wed May 16 2012 - 05:53:48 CDT

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