Considerations for SQL Server Instances and Databases for Virtualization


Virtualization has growing demand and implementation after many success stories. Previously SQL Server instances were installed on servers with their own physical hardware, but that also introduced challenges of effective usage of the available hardware. Over a period of time, the hardware has dramatic changes which made available high configurations for cheaper price and smaller sizes and servers have become more powerful and can support a lot of CPUs, high amount of memory in terabytes, support for high storage, local, SAN and SSDs. So, virtualizaiton helps in using these powerful tools in an effective manner by allowing to create multiple virtual machine guests on one host server, thus making the hardware usage effectively.

With latest virtualization technologies have their own virtualization operating system which is installed on top of hardware even before the installation of the Windows Server Operating Systems. Once the Virtualization OS is installed, now it allows creation of multiple virtual machines each with certain set of CPU, Memory and Storage. Each VM acts as independent server and any operating system can be installed and any applications can be installed, this helps segregate multiple applications running on server server to running each application on its own virtual machine. When it comes to SQL Server, where the SQL Server instances are spreads cross many different servers need to be consolidated and moved into their own virtual machine or combine multiple databases and host them on their own VM and SQL Server instance.

To consolidate multiple SQL Server instances on different physical servers into their own VM ot on to a single SQL Server instance, we will need to follow a proper approach or consider various options to choose what suits the requirement better. Below are some of the options to consider inorder to choose which databases, instances and servers can be consolidated.

Version upgrade paths – Need to understand if we can group the databases which does not have issues upgrading to higher versions as soon as one is available. If the databases cannot be upgraded and requires lot of planning and testing before hand then such databases are better of to have their own dedicated VMs.
Maintenance Windows – Need to group databases which can have maintenance performed at certain time, such can be hosted on same VM and which have different maintenance times, can be moved to their dedicated VMs.
Security – Databases or applications which require high security are better of hosted on their own VMs.
Performance – Critical servers which require high performance can be left running on its own physical hardware or on a server which is shared by non-critical applications to avoid other servers using high amount of resources from the host server.
High Availability – Databases or applications which are very critical and require high availability needs their own dedicated VMs.
Licensing – If licensing cost needs to be reduced, then need to try and group databases with similar characteristics on one SQL Server instance or few SQL Server instances on different VMS.
Backup and Restore – Databases or applications which require very good planning for recovering data and time taken to recover the data is very small, such are to be hosted on own servers.

Hope this was helpful.

This is applicable for below versions of SQL Server

SQL Server 2005
SQL Server 2008 R2
SQL Server 2012
SQL Server 2014
SQL Server 2016

SQLServerF1 Team
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