Our Oracle DBA wants to know if Asynch I/O is enabled

[scb]

Our Oracle DBA wants to know if Asychronous
I/O is enabled on our Solaris 2.6 Sun E6500.
We are running Oracle DB v8.0.6 and v9.0.1,
and he needs to know this in order to
properly tune the database(s).

What is asynch I/O exactly? How to enable it
and verify that it's been enabled and in use?
Can it be used with mounted filesystems
(UFS)? Any gotcha's or limitations with using
or not using AIO? What is KIO, and how does
it relate to AIO (if at all)?

Any help would be appreciated.

Thanks,
SCB

 

[tuka]

Here are a couple of docs which might be helpful.

http://sunsite.nstu.nsk.su/sunworldonline/swol-03-1996/swol-03-aio.html

sunsite.uakom.sk./sunworldonline/swol-07-1998/swol-07-insidesolaris.html

These are taken form from sunworldonline.

 

[tuka]

Another site to look is :

http://www.incad.cz/sun/produkty/software/solaris26.pdf

This is a pdf and search for aio (page 41 of this doc)

 

[jimbopalmer]

AIO Asyncronus Input/Output allows Oracle to use one database writer to write to many Disks, if you do not have AIO, then each Physical Disk should have its own database writer. This obviously consumes RAM and CPU cycles compared to just needing one. (Solaris 2.x defaults to AIOeither with File System or Raw)

KIO Kernal Input/Output puts the Disk I/O routines in the kernal, not in seperate device drivers, this reduces CPU task switching overhead, but not Disk I/O unless the drives are close to the speed of the CPU, which is unlikely. I love everyone til they prove otherwise, sadly some prove otherwise SO quickly

 

[scb]

This is why I'm so confused about AIO,
KAIO, Direct I/O: all the conflicting
information. If we're using mounted
filesystems (UFS), is AIO/KAIO present
by default or not? Is it being used?
What if we're also using RAID Manager
v6.x and Veritas Volume Manager 3.x.x
(not VxVS) on Sun A1000's on this system?
How does this fit into the picture?

Thanks,
SCB

 

[jimbopalmer]

Direct I/O is the ability to use file systems but ignore the unix buffer cache, as the SGA caches Disk I/O. In theory it was added in Solaris 2.6 but I could not make it work, myself. It DOES work in VxFS.

rm6 (horrible name)is fine, you can use it with File Systems and still get AIO, and 20 meg of RAM cache on your disks I love everyone til they prove otherwise, sadly some prove otherwise SO quickly