RE: How to enable Async I/O on Solaris

  I was going to wait until tonight to send out the link to the article(s), but I got a few emails showing interest, so I tracked one of the Sunworld InsideSolaris articles down. I'm pretty sure I have a link to another article at home that explains it a little better, but for those of you that are interested:

http://www.sunworld.com/sunworldonline/swol-07-1998/swol-07-insidesolaris.ht ml

Jeff S

-----Original Message-----
From: Jeffery Stevenson [mailto:jeff_at_mpv.com] Sent: Monday, November 13, 2000 11:06 AM To: Multiple recipients of list ORACLE-L Subject: RE: How to enable Async I/O on Solaris

  Solaris does seem to support AIO in a bastardized manner...I've been doing some research on it at home (which is where I have a bunch of links to articles that discuss it). Basically, the kaio system call gets posted and on a raw system works fine...on a cooked system it generates the same error message a few times. Digging a little deeper on this (after reading through an article on the subject...I'll have to post that to the list tonight), I noticed that each error created a new light-weight process thread that started doing other work. These lwp threads would each run their course and then generate a normal write system call (pwrite64 in the more recent versions of Solaris). If you take a look at the system calls from the DBW0 process, it just looks like the asynchronous I/O call (kaio) is just failing and then reverting to normal writes, but if you look at the lwp level, you can see that each one of these is being handled by multiple lwps. It is essentially a "mock" asynchronous I/O, and it's probably not as efficient as creating multiple DB writers like Gaja suggests, but it does seem to work. I'll try to send the article out to the list later on if anyone is interested. It is basically a Sun article that explains in more detail how this mock AIO works. Just some more stuff to think about...

Jeffery Stevenson
Chief Database Geek
Medical Present Value, Inc.
Austin, TX

-----Original Message-----
Sent: Monday, November 13, 2000 9:50 AM
To: Multiple recipients of list ORACLE-L

It is supported for raw devices and Quick I/O Veritas files.

-----Original Message-----
Sent: Friday, November 10, 2000 5:26 PM
To: Multiple recipients of list ORACLE-L

Jared,

Do you mean it works pretty bad or it is not supported on Solaris? Does it work on Solaris at all?

Thank you,
Michael
www.atelo.com

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Friday, November 10, 2000 16:39

> On Fri, 10 Nov 2000, Bill Conner wrote:
>
> > At 11:30 AM 11/10/00 -0800, you wrote:
> > >The default for disk_async_io is true.
> > >
> > >Either async i/o is support or not. T'ain't supported on
> > >Solaris unless you have raw devices.
> >
> > This is news, solaris used to support async i/o on cooked
> > devices when did this change?
>
> Well, it's never actually worked on cooked filesystems.
>
> Jared
>
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> Author: Jared Still
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