The data-base data and log files for each virtual server
are typically installed on a shared storage resource
that is dedicated to that virtual server.
The primary node for each virtual server runs on separate hardware,
as shown in Figure 32-2.
Because there are multiple instances of SQL Server 2005 running on each instance,
a separate SQL Server 2005 license is required for each virtual server.
You can use a multinstance cluster to scale out database solutions
to separate hardware resources.
It is more cost-effective than a single-instance cluster
because it utilizes all of your existing hardware.
The HR and Sales databases shown in Figure 32-2 effectively run
on separate hardware resources and are therefore able to individually fully utilize
the memory and processor resources available.
Note:
In case of a failover,
you need to ensure that each node has the required memory and processor resources
to maintain any existing SLAs, as one node will now be running two instances of SQL Server 2005.
You can take advantage of SQL Server 2005's dynamic configuration options
to allocate appropiately in case a failover occurs.
Source: Microsoft SQL 2005 Administrator's Companion,
Page 1094-1095