Re: Intelligent Data Placement - IDP question regarding using this for different physical devices

From: Kevin Jernigan <kevin.jernigan_at_oracle.com>
Date: Thu, 15 Aug 2013 00:22:19 -0400
Message-ID: <520C577B.50906_at_oracle.com>



Rumpi,
I assume you're referring to the IDP feature of ASM. I checked with ASM product management, and they responded:

Unfortunately, IDP does not work the way the OP envisioned. IDP allocates within a single device using low-ordered LBA ranges as higher performance. It is typical that for standard rotating disks, low ordered LBA accesses offer better performance than higher-ordered LBA ranges. Furthermore, this is not even true for SSD-based devices. I invented the concept of IDP before SSD devices were common place. IDP does not cause preferential allocation across different device classes. Consequential, this scheme will not work...

However, in Oracle Database 12c, the Heat Map and Automatic Data Optimization (ADO) features are designed to do exactly as you describe. You can set up ADO policies on a tablespace to cause the coldest partitions in that tablespace to be moved to a different tablespace, presumably on more cost-effective storage, when the original tablespace becomes too full based on a threshold you can set. You can also create ADO policies that compress data based on Heat Map-collected data, and you can even create custom conditions for your ADO policies, to trigger movement or compression of data based on any conditions that you can code in a PL/SQL function.

Are there specifics to your scenario where this approach doesn't help (other than the likelihood that you haven't upgraded to 12c yet)?

-KJ

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Kevin Jernigan
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On 8/14/13 3:00 PM, Rumpi Gravenstein wrote:

> We have purchased SSD storage for our servers . This storage is assigned to
> UNDO, Flashback Archive and TEMP. Unfortunately we now need more space and
> have max'd out our ability to add SSD storage to the server.
> An approach we are considering is to use IDP to effectively "extend" our
> SSD devices assigning our existing SSD storage to HOT and adding additional
> SAN storage as COLD.
>
> So here's the question -- has anyone looked at IDP and how well it manages
> the HOT/COLD assignments. Ideally we would want HOT areas to completely
> fill before we spill over to cold. I'm also interested in general thoughts
> on using IDP in this way.
>
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Received on Thu Aug 15 2013 - 06:22:19 CEST

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