Re: 10g - ASM

Lisa:

I haven't run ASM on Windows. Howevever, on Unix platforms it uses the raw device, meaning that it has direct access to the disk. In the case of your SAN, that would mean the "logical disk" as it is presented to the node. In theory, that should be a distinct physical disk but in the world of storage virtualization that is not always the case. Having said that, if Oracle thinks that two "disks" are distinct and they are actually different views of the same physical disk, then this can cause ASM to make some poor performance-related decisions regarding its striping and mirroring.

I have experimented with it, but haven't tried to implement it in any kind of production capacity. Some of the major arguments put forth for the use of ASM include the ability to easily add disks, distribute I/O's, stripe, mirror, etc. all maintained and handled by the database. I can see some advantages for the small shops where they want to allocate a pool of disks and leave Oracle to run on them without all of the disk fine-tuning, but I am not convinced about larger enterprise configurations where you're trying to squeeze every last drop of juice out of the lemon. I am still on the fence and haven't developed a religious feeling about it yet as I am still studying the implications.

Hope this helps a bit.

Koivu, Lisa wrote:

>Hello all,=20
>
>I'm currently installing 10g on Windows 2003. Anyone using Automatic
>Storage Management? =20
>
>I read this in the ASM documentation (below), and I'm concerned because
>a LUN is a logical volume. I wonder if implementing ASM is just an
>unnecessary pain for a SAN environment, especially considering the
>enormous SAN cache. =20
>
>Way back when I didn't have grey hair and I worked on Unix, all my
>devices were logical volumes. That was standard in every Unix shop I
>worked in. I get the feeling I'm missing something or misinterpreting
>this paragraph below. It sounds like it wants direct access to disks,
>period.
>
>I am not a SAN, Unix or Windoze expert. Comments, anyone? =20
>
>Thanks
>
>
>
>With Automatic Storage Management, the definition of the logical volumes
>of a storage array is critical to database performance. Automatic
>Storage Management cannot optimize database data placement when the
>storage array disks are subdivided or aggregated. Aggregating and
>subdividing the physical volumes of an array into logical volumes can
>hide the physical disk boundaries from Automatic Storage Management.
>Consequently, careful consideration of storage array configuration is
>required.
>
>
>Lisa Koivu
>Sr. Monkey
>Orlando, FL, USA
>
>
>
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Byron Pearce                         mailto:pearceb_at_tenure.com
Tenure Systems, Inc.                 Dallas/Fort Worth, TX

"It's hard to be a ninja when you wear a beeper."



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