VMWare permits network and database administrators to partition hardware resources (processors, memory, etc.) in mid- to large-scale servers into virtual servers. This partitioning technique was common on the mainframes as well as in the Unix community and is being adopted in the Windows world. With mid- to high-scale caliber of equipment, it is sometimes beneficial to split the resources to best address the business needs. One technique can be to split the resources across numerous applications that become independent of one another although they reside on the same piece of hardware. In reality each virtual server is independent of the others and is managed as any other server although the hardware is shared, which can be 100% unknown to the users. As far as problems are concerned, this technology is being adopted at many organizations with the recent trend of managing less large scale servers as opposed to many smaller scale servers. If a performance problem should occur, the problem should be isolated to the virtual server and not affect the remainder of the virtual servers.
Another technique organizations are leveraging is installing multiple instances of SQL Server, up to 16, on a single Windows server. It is possible to partition some of the resources (processors, memory, etc.) and manage each SQL Server instance independent of the others. This technique is being leveraged in ISP/ASP scenarios where a single server is shared between multiple clients and each client is able to have full rights to the individual SQL Server instance without knowledge of the remaining instances and only pays for a portion of the resources as can be the case with the VMWare servers.
Multiple instances can also be beneficial in development environments where it is beneficial to have numerous independent environments for a team of developers. The same is true when it comes to testing; the multiple instances provide an opportunity to test the code base in multiple instances simultaneously, which can be beneficial for functional or regression testing. Both options offer organizations and IT professionals greater flexibility and are licensed in a cost effective manner from Microsoft. Consider both options as you move forward with your applications to reap the benefits of the improved flexibility in your development, test and production environments.
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This was first published in January 2004