RE: Async and Direct I/O On Solaris using VXFS

From: Jorgensen, Finn <>
Date: Tue, 28 Jun 2011 08:33:47 -0400
Message-ID: <9CE162BC5ED2C643956B526A7EDE46FF02693F38E8B8_at_EXM-OMF-04.Ceg.Corp.Net>

I've done a fair amount of testing on Solaris and VxFS. I wouldn't call it exhaustive at all so you should do your own testing.

What I've found is that VxFS does not allow async IO regardless of what you do. Even ODM does not enable AIO. It enables directio without setting filesystemio_options and without setting convosync and mincache which has implications when accessing files in the filesystem outside Oracle (like a cp or mv). ODM, by the admission of a Sr Technical engineer from Veritas, is mostly good for certain types of scenarios. It wasn't worth the changes required and the amount of testing necessary in my environment. The one thing that really made a difference for me was setting a kernel parameter called vmodsort(set vxfs:vx_vmodsort=1 in /etc/system). This parameter makes the fdsync kernel call a lot faster which really cut down on the CPU utilization on the servers and made IO a lot faster especially for apps using LOBs.


From: [] On Behalf Of rajesh koppada Sent: Monday, June 27, 2011 6:29 PM
Cc: Posting
Subject: RE: Async and Direct I/O On Solaris using VXFS

Thank you , sorry i missed the platform information , We are running on Sun Soalris 5.10 , Is there a similar way we can confirm that we are doing Async i/o ? or do we need to use special products like Oracle ODM or something to get Async i/o ?

Date: Mon, 27 Jun 2011 15:17:12 -0700
Subject: Re: Async and Direct I/O On Solaris using VXFS

The tool "directiostat" looks pretty cool for sparc, on page

direct link at

On Mon, Jun 27, 2011 at 2:57 PM, kyle Hailey <<>> wrote:

What platform are you on? For direct I/O on solaris check out


Another good reference<>

2011/6/27 rajesh koppada <<>> Hello,

How can i confirm that oracle will be doing Direct I/O and Asynchronous i/o with following options. Database FILESYSTEMIO_OPTIONS is set to ALL which means to use, setall - Enables both ASYNC and DIRECT IO we are using VERITAS volume manager 5.0 with VXFS filesystems(We don't have QIO or ODM) and file system mount options are set as follows mincache=direct and conovsync=direct
Will Oracle is going to use both direct i/o and asynchronous i/o with these file system options. How can we ensure i am getting direct i/o and Async i/o ? can we enable some trace or something just to ensure we are getting both?


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Received on Tue Jun 28 2011 - 07:33:47 CDT

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