Re: Fw: VxFS threaded AIO vs. DBWR Slaves

You say you are building a new database, so you probably dont even know if you have dbwr problems correct? Usually one dbwr does quite good job unless your application is very write intensive.

In HPUX and vxfs you should look at direct i/o instead of aio

Thanks

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LSC


On Wed, Feb 27, 2008 at 10:54 PM, Charlotte Hammond <
charlottejanehammond_at_yahoo.com> wrote:



> Hi All,

>

> On further research it would seem that threaded Async I/O is a property of

> Solaris, not of VxFS.  And that HP-UX doesn't share that feature.  (Please

> let me know if I'm still getting it wrong!)

>

> Therefore, since I'm stuck with HP-UX on VxFS, I'll look at the

> DBWR_IO_SLAVES option.

>

> Thanks for all who replied!

>

> Charlotte

>

>

> ----- Forwarded Message ----

> From: Charlotte Hammond <charlottejanehammond_at_yahoo.com>

> To: Greg Rahn <greg_at_structureddata.org>; oracle-l_at_freelists.org

> Sent: Tuesday, February 26, 2008 9:24:45 PM

> Subject: Re: VxFS threaded AIO vs. DBWR Slaves

>

> Hi Greg,

>

> Thanks for the tip.  Unfortunately I'm not in a position to dictate ASM at

> present and have to live with what I've got (at least for now!).

>

> Somebody mentioned off-list that threaded AIO may not be a feature of VxFS

> on HP-UX (although I believe it is on Solaris).   Can anyone confirm or

> refute?  I'm finding it hard to get a definitive answer on this.

>

> Assuming that threaded AIO *does* exist and that I *do* want to use it,

> should I just set FILESYSTEMIO_OPTIONS=SETALL and DISK_ASYNCH_IO=TRUE as if

> it were kernelized AIO?

>

> Thanks You!

> Charlotte

>

>

> ----- Original Message ----

> From: Greg Rahn <greg_at_structureddata.org>

> To: charlottejanehammond_at_yahoo.com

> Cc: oracle-l_at_freelists.org

> Sent: Monday, February 25, 2008 10:09:29 PM

> Subject: Re: VxFS threaded AIO vs. DBWR Slaves

>

> I would suggest using ASM.  Then you can leverage all the benefits and

> not have to worry about file layout.

>

> If you use threaded async or emulate async by multiple db writers, its

> probably the same overhead.

>

> On 2/25/08, Charlotte Hammond <charlottejanehammond_at_yahoo.com> wrote:

> > Hi All,

> >

> >  I'm building a 10g database on a VxFS filesystem on HP-UX.  I

> understand this does not support kernelized asynchronous I/O but does

> support threaded asynchronous I/O which I believe has a significant CPU

> overhead.  So: should I use the threaded asychronous I/O from VxFS

> (FILESYSTEMIO_OPTIONS=SETALL) or should I switch it off, and use multiple

> database writer slaves instead?

> >

> >  My aim is targeted towards performance rather than capacity (i.e. small

> number of users in database).

>

>

> --

> Regards,

>

> Greg Rahn

> http://structureddata.org

>

>

>

>

>

>

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