RE: ASM mirroring vs SAM mirroring

Hi Tony
 
Your information is much appreciated.
 
From all the HP Papers it was never clear about such stuff, I guess you had to 
have the presentation with them.
 
Now I can at least make plans around those requirements
 
It seems from things I had heard about that some other technologies supposedly 
allow you to do both mirror at teh HW level and ASM.
 
Will have to consider this information in regards to the DR plans and test this 
failure out. This is still being implemented and have time to desing the 
document on failures if they should occur.
 
Cheers
 
Peter

________________________________

From: Tony van Esch [mailto:tvesch@xxxxxxxxx]
Sent: Fri 27/07/2007 8:12 PM
To: Peter McLarty
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: ASM mirroring vs SAM mirroring



Hi,

we have a similar config running (DUAL HP EVA, mirroring and RAC) and
asked the suppliers (HP & Oracle) what would be a certified solution. In
the end ASM was the only viable solution.


1> mirroring on SAN level with EVA is called 'Continuous Access'. You only
get presented the primary LUN's, but not the copy. The copy is NOT
presented to the racnodes. So if the storagebox/site with the primary
LUN's fails, you lose your disks and your database is gone and you have
downtime. Not really flexible. the mirror woulf have to be presented to
the racnodes to get things up & running.

2> Mirroring with ASM (host-based mirroring). Is this case the primary and
the copy are both presented to the racnodes and placed inside the correct
failuregroups (FG1=site1/storagebox1 and FG2=site2/storagebox2). If one
storagebox/site fails, only one failuregoup is lost, but the database will
still be available.

So if you distribute racnodes of one cluster over two datacenters
mirroring for the databases should be done with ASM. I'm even not sure
Continous Access is supported for shared storage.

regards,
Tony van Esch



> Hi all
> Not being a storage guru, I need some help
>
> I have been through the papers on racsig and done some googling "asm
> mirroring" and looking for product specific papers and cant find
> anything definitive as to why one is a winner and not the other
>
> Here is my scenario
> 2 HP EVA8000 SANS
> RAC cluster
> ASM for storage on said SANS
> The two SANS are in different datacenteres about 1km apart.
> Some cluster nodes reside in each datacentre.
> Oracle 10.2.0.3 Redhat 4 nodes
>
> Question is ASM mirroring better than SAN mirroring? Why is it better or
> not  Sould we use the HP SAN mirroring product
>
> Cheers
>
> --
> Peter McLarty
> Database Administrator
> Student System Upgrade Project
> Central Queensland University
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>




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