Multi-Tenancy and Resource Management

As my association turns 24years today with the computer software; most of the past year I have spent on Oracle Exadata - An appliance (with hardware + software bundle of specified configuration as 1/4 rack, 1/2 rack or a full rack)

In the pre-appliance world, the underlying deployment architecture of server, network, storage would be built as per the application requirements and the quality attributes are "portability", "scalability" and so on....

An application would be sized for the capacity of required CPU, Memory, I/O, storage along with its local fail-over requirements and the disaster recovery requirements and the underlying infrastructure was built using either physical or virtual components of server(s) and storage. The number of nodes in the cluster and size of each node would be carefully planned.

But, with the Exadata, the pre-configured 8 compute nodes with 14 storage cells in a full rack is configured by Oracle. Each compute node has 24 CPU cores and 96GB of memory.

Now this Exadata appliance need to be shared by multiple applications.. The complexity of multi-tenancy starts here. How to ensure Quality of Service?

1. Server pools and Instance Caging
2. Service design
3. Database Resource Manager
4. I/O Resource Manager

I think it is always good to have a database per application. Hosting multiple applications on a single database instance could be tricky with respective to the CPU allocation.

Next most challenging task is allocating the memory across multiple applications. This is one thing it is still being done manually. Automatic SGA and PGA management and memory tuning within an instance is improving but allocating a memory target for each database should be done manually.

Classifying the workload within a database using the USER NAME, SERVICE, CLIENT PROGRAM NAME, CLIENT USERNAME, MODULE, ACTION etc., parameters to a "resource consumer group" and assigning a resource consumer group to a resource manager plan is achieved using DBRM. Every user session should be put on the right consumer group dynamically based on multiple parameters rather than always putting USER1 on medium_consumer_group. If USER1 is performing an important action that session should be prioritized at a higher level.

Finally, controlling IO operations on the cells across the databases and multiple workloads from within a database also a very important activity to maintain the right Quality of Service (QoS). IO Resource manager database plan and a category plan for prioritizing the workload from within a database should be configured.

In my opinion, the performance management within the appliance world has become more complicated due to the complexity involved in the QoS and resource management. Now we have to develop applications that are best suited to use the platform features of the appliance like Exadata.

Questions to think about:
Is this going opposite of "portability"? How easy is it to port the applications from one appliance to another?