May 28, 2004 at 5:31 am
I am installing 4 virtual servers in a 2-node active/passive failover cluster.
Previously I have read the following statement in Microsoft sourced document :-
"You can run only one instance of SQL Server on each virtual server of a SQL Server failover cluster, although you can install up to 16 virtual servers on a failover cluster. The instance can be either a default instance or a named instance. The virtual server looks like a single computer to applications connecting to that instance of SQL Server.........."
I interpreted this to mean that, if I wanted to, I could have 3 virtual servers installed as default instances and the fourth one as a named instance.
However, when I tried to install a second virtual server as a default instance, I found the check box greyed out and I was only allowed to create a named instance.
I know that you are only allowed one default instance in a 'standalone' installation of multiple instances.
I suppose my basic question is "what exactly IS a virtual server ?"
Each of my virtual servers has a unique IP Address but common subnet.
Could it be that each virtual server would need to be on a different subnet, with separate interface card etc to be able to have more than one default instance?
I would be grateful for any help, maybe I have just misunderstood the documentation.
May 28, 2004 at 7:38 am
Let me try to clarify based on my experience with multiple instances on a cluster. First, I think you are confusing instances with virtual servers, in that any instance built on a cluster would be considered a virtual SQL Server, or instance.
A virtual server is a highly scalable and highly available server built on a cluster of real servers. The architecture of cluster is transparent to end users, and the users interact with the system as if it were only a single virtual server.
So, when you say virtual servers, you mean SQL Servers? Otherwise, a virtual server is one that is created across multiple nodes, in your case two.
On top of the virtual server, like any server, you can, according to MS, create up to 16 instances - one is the default, the others would be named instances. When you install SQL Server on top of the cluster, it is as if you are creating it on one server, and will recognize if a default instance was already created.
However, each SQL Server instance,as you know requires its own IP address, and port number.
Also, keep in mind, that with multiple instances on a cluster, or any server for that matter, will compete for resources, so best to have as few as possible, w/o having to acquire 3rd party resource managers.
Hope this helps!
May 28, 2004 at 8:25 am
Just another piece of food for thought, rather than have a 4 instance active/passive make it a 4 instance active/active with 2 instances running on each node, you'll get far better performance and less problems with resource contention.
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