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Re: ASM question

From: Alex Gorbachev <gorbyx_at_gmail.com>
Date: Sun, 25 Feb 2007 17:56:00 -0500
Message-ID: <c2213f680702251456y61d27f8dk6b04fa5f3fa47db6@mail.gmail.com>


Greg,

See few notes inline.

On 2/24/07, Greg Rahn <greg_at_structureddata.org> wrote:
> To quote the documentation:
> http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14231/storeman.htm
>
> for normal redundancy:
> FREE_MB - REQUIRED_MIRROR_FREE_MB = 2 * USABLE_FILE_MB
> or
> (FREE_MB - REQUIRED_MIRROR_FREE_MB)/2 = USABLE_FILE_MB
>
> Using the below example's numbers:
> (20374 - 5120)/2 = 7627

Oracle documentation you quoted only confirms that those calculation are valid when every disk is in each own failure group (default): "The following query shows capacity metrics for a normal redundancy disk group that consists of six 1 GB (1024 MB) disks, each in its own failure group."

The case with many disks in two failure groups is a special case and this formula is incorrect.

> At this point I'm going to recommend reading the Metalink note 395712.1
> because there is a similar example worked out as well as some other
> useful questions & answers.

Looks like ML Note 395712.1 is non-public.

> I would also agree that external mirroring may be more simple. There
> isn't even a need for Veritas as a lvm. Just RAID it on the DMX3000.

If you are mirroring over different storage boxes than host based mirroring is the way to go. Perhaps, some storage vendors provide cross boxes mirroring.

-- 
Best regards,
Alex Gorbachev

http://www.oracloid.com
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http://www.freelists.org/webpage/oracle-l
Received on Sun Feb 25 2007 - 16:56:00 CST

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