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VxFS tunables for Oracle on HP/UX

From: Jesse, Rich <>
Date: Mon, 12 Apr 2004 12:23:13 -0500
Message-ID: <>

Hey all,

In implementing a SAN on a new HP/UX 11.11 system, I'm not particularly blown away by the I/O performance from Oracle or otherwise, with or without the 2GB writeback caching. So, I'm looking to see what our tunables are.

One batch of tunables are the VxFS "vol_xxxx" kernel parameters. Has anyone messed with these for maximizing I/O performace for Oracle? In particular, it seems that the default value for "vol_maxio" may be inadequate for Oracle, but I haven't been able to find a definitive guide as to how to determine a proper value. The Most Venerable Gaja has some references to this in his "Implementing RAID on Oracle" whitepaper (, but the calculation of the value of vol_maxio is a little vague, suggesting either 2048 or 8192, but not being definitive as to how to determine which is "better" (pages 16-17 of the whitepaper).

I also found an HP-UX guide to the "vol_xxxx" parameters at, but there are no suggested values for vol_maxio and most other params. One thing it does say is that "The value of voliomem_maxpool_sz must be at least 10 times greater than the value of vol_maxio." But since the UOMs are different between the two params -- vol_maxio is in 512-byte blocks and voliomem_maxpool_sz is in bytes -- it doesn't say if the specified value is to be 10 times greater or if it's the number of bytes that's supposed to be 10x.

I need to keep in mind that VxFS is used both for DBs on the SAN as well as software and other files on the local SCSI drives. I imagine that the DB I/O performance would be more important, though.

Thoughts, anyone?

Rich Jesse                        System/Database Administrator      QuadTech, Sussex, WI USA

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Received on Mon Apr 12 2004 - 12:23:00 CDT

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