Async I/O setup in HPUX

[Manikrajan]

Could Async I/O be setup for a filesystem which has Oracle database and will it increase the performance of the database?The server has HPUX11iv3.

[Avinash20]

You answer lies here:
www.docs.hp.com/en/11iv3IOPerf/IOPerformanceWhitePaper.pdf

[Jeeshan]

It should be recommended by Oracle.

Surely it could increase the performance of the database but actually depends upon the size and load of the database.

One more thing, async I/O could not ensure you the data integrity.

[Avinash20]

Also please remember to assign points to the threads once you get your answers
http://forums11.itrc.hp.com/service/forums/helptips.do?#33

[Duncan Edmonstone]

The only way to run Oracle async IO on a filesystem on HP-UX, is to get one of the Serviceguard Storage Management Suite editions which includes ODM (Oracle Disk Manager). This allows you to enable async IO. Read about it here:

http://docs.hp.com/en/10404/ODM_SingleinstanceOracle.pdf

Otherwise async IO requires raw rather than cooked IO (i.e. no filesystem). As Oracle have already indicated they are going to deprecate completely raw IO in Oracle 12g, this implies using ASM (which is very annoying as ASM is still a pretty immature product in my opinion).

Of course instead of doing async IO you could just run more than one DBWR and acheive broadly the same result...

HTH

Duncan

[Steven E. Protter]

Shalom,

Posted:
>>>>>
The only way to run Oracle async IO on a filesystem on HP-UX, is to get one of the Serviceguard Storage Management Suite editions which includes ODM (Oracle Disk Manager). This allows you to enable async IO. Read about it here:
<<<<

I do not believe this to be the case. I ran asynchronous I/O for oracle on HP-UX 11.11 servers in the US, cooked file system.

It required some special configuration.

It will if implemented improve performance.

Docs:
http://archives.devshed.com/forums/databases-139/enable-asynchronous-disk-i-o-on-hp-ux-400848.html

http://www.docs.hp.com/en/11iv3IOPerf/IOPerformanceWhitePaper.pdf

http://hpux-tips.blogspot.com/2006/01/how-to-enable-asynchronous-io-disk-hp.html

Middle link is the best IMO. It may prove me wrong, but the answer is there.

SEP

[Duncan Edmonstone]

Well I'm pretty sure you *can't* do it...

But I'm happy to be proven wrong...

Let me quote some items from Oracle Metalink document 139272.1:

--------
Before deciding on one of these two options, it should be noted that on HP-UX,
aio is *only* possible on a raw device. Put in another way, aio *cannot* be used
on a filesystem.
--------

SEP, you might be thinking of setting the fs_async parameter, which is supposed to enable async IO for filesystems, but from the same metalink article:

--------
The kernel parameter fs_async can be set to allow asynchronous writes to file
systems. However, write calls can return without the data being physically
written to disk (the write sits in the UNIX buffer cache). The data in question
is file-system metadata such as free space lists, blocks and inodes.
A system crash would potentially lose this data, and leave the filesystem in an
inconsistent state, causing database corruption.

Oracle still opens files with the O_DSYNC flag (see 'tusc' snipet
below), which insists that writes are physically written:
open("/oracle/datafiles/system01.dbf", O_RDWR|O_LARGEFILE|O_DSYNC, 0) = 19

In summary, fs_async is ignored for datafiles(due to open() with O_DSYNC).
However, filesystem metadata may be lost, potentially causing datafile
corruption.
--------

Also see this part of the admin guide for 10g:

http://download.oracle.com/docs/cd/B19306_01/server.102/b15658/appb_hpux.htm#i637036

HTH

Duncan