Re: VLDB ASM & SAN Striping Question

  • From: Matthew Zito <matt@xxxxxxxxxxxxxxxxx>
  • To: ChrisDavid.Taylor@xxxxxxxxxxxxxxx
  • Date: Wed, 6 Jun 2012 11:38:21 -0400

I haven't poked around the EVA line in a while, but if I remember
correctly,what you describe is basically impossible in an EVA.  The
way an EVA works, you make a disk group, and all of the LUNs in that
disk group are dynamically striped across the disks in that group.
You could theoretically make a 2-disk group, and one LUN from those,
but I *think* you have to assign hot spares to individual disk groups,
and hence you'd burn a lot of storage just on spares in that

What you could do is ask them to make sure that when you add a new
LUN, it comes from a different disk group than the current LUNs.
Probably your best bet.


On Wed, Jun 6, 2012 at 8:22 AM, Taylor, Chris David
<ChrisDavid.Taylor@xxxxxxxxxxxxxxx> wrote:
> I am curious if anyone on this list has worked on disk striping at the SAN 
> layer and then at the ASM layer?  Specifically, I want to know if you drilled 
> all the way down to the physical devices on the SAN (controllers and physical 
> disks) to make your hardware stripes?
> In the my current IT dept (and in my previous one) the SAN administrators 
> weren't SAN experts (no fault of theirs) and I was told they couldn't stripe 
> disk groups across specific controllers and specific disks (meaning they 
> didn't know if it was possible and if it was they didn't know how to 
> accomplish it).
> I was reading the Oracle doc "Oracle Database VLDB and Partitioning Guide 11g 
> Release 2 (11.2) at: 
> when I 
> saw this paragraph:
> "Oracle ASM can be used on top of previously striped storage devices. If you 
> use such a configuration, then ensure that you do not introduce hot spots by 
> defining disk groups that span logical devices which physically may be using 
> the same resource (disk, controller, or channel to disk) rather than other 
> available resources. Always ensure that Oracle ASM stripes are distributed 
> equally across all physical devices."
> I understand striping really well.  What I'm having a hard time is finding 
> the "how" in creating LUNS across specific controllers and only specific 
> disks attached to those controllers in a typical SAN (specifically we're 
> using an HP EVA 8100).  Who of you have actually done this - drill down to 
> the controllers and devices and how hard was it to convince the SAN 
> administrator to help accomplish this?
> Any input and thoughts are appreciated.
> 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.
> --

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