RE: Concurrent I/O (AIX 5.2)

We had a good experience, but it was during an implementation of a new server so there wasn't a whole log of pre-CIO data to compare to, however we did do some before/after testing and had improvement with CIO but it is critical that you also increase your db_cache_size when you do this, and this also makes it difficult to compare apples to apples - because obviously increasing your db_cache_size can improve performance regardless of CIO. You are basically stealing the cache away from the OS level where Oracle would have reported incredibly fast physical reads because they were in fact not physical at all, but were cached by AIX - so you have to replace that with more cache for Oracle (we increased db_cache_size from 800MB pre-CIO to 2GB post-CIO)

I have since implemented a 2nd system with CIO and this time didn't even do a pre-CIO comparison - just went with it from the beginning and performance has been excellent. Also, be sure to set agblksize=512 for you redo log filesystems, set filesystemio_options=setall and verify your filesystems are mounted with o=cio if using 9i.

Regards,
Brandon

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Stuart Clowes Sent: Wednesday, June 28, 2006 1:07 PM
To: oracle-l_at_freelists.org
Subject: Concurrent I/O (AIX 5.2)

We bit the bullet and implemented concurrent I/O (AIX 5.2 ML6, 9.2.0.5, JFS2, ESS storage).

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