Re: Matching storage stripe size with ASM allocation unit?

From: K Gopalakrishnan <>
Date: Sat, 24 May 2008 23:45:16 -0500
Message-ID: <>


Reducing AU size is unsupported. Apart from that, ASM shared pool (and sometimes DB instance shared pool) has to keep lot of extent pointers (for lack of better ASM terminology) in the shared pool and it will incrase the chance of 4031 along with performance degradation in ASM operations.

Did you have a chance to read Nitin's ASM handbook. You will understand what I am talking here.


On Fri, May 23, 2008 at 11:26 AM, Yong Huang <> wrote:
> I heard an Oracle consultant suggest that the storage should be created with
> stripe size 1M for ASM, because the default ASM allocation unit (probably
> _asm_ausize) is 1M. He says most shops have much smaller stripe size. I asked
> since it's too late for the storage team, what if we lower our ASM allocation
> unit size? He gives no comment except he doesn't recommend.
> Now I think about it. The ASM 1M allocation unit is for allocation or
> deallocation. It can't be I/O chunk size, which is still from db_block_size up
> to that multiplied by db_file_multiblock_read_count. The ideal stripe size may
> be typical I/O size dictated by the most frequently run SQL divided by number
> of disks in the striping setup (or larger than that). The ASM 1M size only
> plays a role when you create, resize or drop a datafile, not normally done
> anyway. Comments are welcome.
> Yong Huang
> --

Best Regards,
K Gopalakrishnan
Co-Author: Oracle Wait Interface, Oracle Press 2004

Author: Oracle Database 10g RAC Handbook, Oracle Press 2006
Received on Sat May 24 2008 - 23:45:16 CDT

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