Using SQL Instances to manage resources for a combined OLTP/OLAP server

I am setting up a SQL 2008 R2 two node cluster for an existing database server that currently supports 6 databases (30-35 gb total), most of which are OLTP type databases supporting front end web based apps that receive about a million hits a year. One of the databases is an OLAP type and I am wondering if by creating two SQL Instances, one for OLTP and one for OLAP, I might better manage resource allocation between the OLTP and OLAP databases. Priority would be given to the OLTP databases, which are more critical to operations. Additionally, I am wondering if this approach would work for a given OLTP database that required priority access to resources. As I also have the opportunity to configure the SAN from scratch I would be able to allocate dedicated disk resources to the individual instances.
aubeyAsked:
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AnujConnect With a Mentor SQL Server DBACommented:
If you are opting single instance, I would recommend to consider SQL Server resource governor, which allows you to distribute the CPU, Memory according the workload. You said that priority should be given to OLTP, so you can configure resource governor so that 70%  (an example) of CPU and Memory to OLTP workload based on the classifier function(Resource governor component, it can be username, appname etc).

If you are considering multiple instance, you should configure the min and max server memory settings and processor affinity properly to improve performance. eg suppose you have 100 GB memory on the server and since your priority is OLTP and you decided the 70% of ram should be given to OLTP instance, then you should configure the max server memory on the OLAP instance as 30GB and OLTP should be 100 or 70, this allows the OLAP instance to use only 30 GB of the memory, and the rest should be given to OLTP instance.

I would recommend, single instance multiple database also, note that in both the options
you should database files should reside in its own disk to overcome disk bottleneck.
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Marten RuneSQL Expert/Infrastructure ArchitectCommented:
Resource govenor does not handle instances.
Therefore I would recommend the same instance, resource govenor for handling resources and different san luns for the oltp / olap databases.
The key is going to be CPU and this can be controled with resource govenor.

Regards Marten
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Marten RuneSQL Expert/Infrastructure ArchitectCommented:
Need further assistance, or clarifications?

Regards Marten
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