From: "Taylor, Chris David" <ChrisDavid.Taylor@ingrambarge.com>
To: 'Matthew Zito' <matt@crackpotideas.com>
CC: "'oracle-l@freelists.org'" <oracle-l@freelists.org>
Date: Wed, 6 Jun 2012 11:18:42 -0500
Subject: RE: VLDB ASM & SAN Striping Question
Thread-Topic: VLDB ASM & SAN Striping Question
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Reply-To: ChrisDavid.Taylor@ingrambarge.com

Okay - now I'm following.  My apologies.

So the key is to focus on disk groups - and in a different product, a SAN administrator should be able to identify specific disks easily to assign to a disk group?  I would assume this would follow to controllers as well?

Something like this:

1. Identify Controllers (primary controllers as I assume more than 1 controller can control the same disk in case of failure in the controller?)
2. Identify Disks attached to that controller
3. Create DG from those disks attached to that controller

*OR* would it make more sense from an IO perspective to:

1. Identify Controllers
2. Identify Disks attached to all controllers
3. Create DG from disks from each controller (instead of disks on 1 controller?)

I'm imagining a scenario like:

Disks 1,2,3,4 on controller1
Disks 5,6,7,8 on controller2

Create DG#1 on Disks 1,5 instead of Disks 1,2 to spread IO across both the disks and the controllers?


Chris Taylor

"Quality is never an accident; it is always the result of intelligent effort."
-- John Ruskin (English Writer 1819-1900)

Any views and/or opinions expressed herein are my own and do not necessarily reflect the views of Ingram Industries, its affiliates, its subsidiaries or its employees. 


-----Original Message-----
From: Matthew Zito [mailto:matt@crackpotideas.com] 
Sent: Wednesday, June 06, 2012 11:13 AM
To: Taylor, Chris David
Subject: Re: VLDB ASM & SAN Striping Question

Right, and my point was just that when you create a disk group, every LUN gets striped across *all* of the disks.  So the right way to handle this is to just request a 1 LUN = 1 DG mapping, that way, when you stripe across LUNs you're guaranteed to be on different disks.

However, odds are, you have a giant disk group, and are making LUNs out of that disk group.  There is no way, in an EVA, to say, "Map this LUN to just these two disks in the disk group".  Everything is striped across all disks in the disk group.

With these kinds of arrays, it is almost impossible to attempt to optimize at an Oracle level for physical placement, and in my experience, it is almost never worth the effort in terms of time and cost.

Matt

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