Virtualization of the Database Role

The SQL Server database role is the last but most challenging server role to virtualize. The server with the database role (otherwise known as the database server) needs the lion’s share of RAM and processor allocation. A minimum of four virtual processors and 8GB of RAM should be allocated to the database server. For best performance, though, at least 12GB of RAM should be allocated.

Like SharePoint VMs, SQL Server VMs require either fixed-sized or pass-through VHDs. The same disk considerations that apply to physical SQL Server machines apply to virtual SQL Server machines. So, be sure to allocate enough disk spindles for the database and logs volumes. In addition, be sure to follow standard best practices for SharePoint–SQL Server optimization, such as presizing the tempdb and moving it to fast disk volumes.

Keep in mind that these guidelines are simply guidelines. Actual performance will be dictated by the type of disk, hardware architecture, and other factors. Some organizations calculate their hardware requirements and then just add RAM or reduce the number of databases on a single SQL Server session.

Microsoft supports both SQL mirroring and clustering as high-availability options in a virtualized SQL Server environment. In addition, host failover options such as Hyper-V Live Migration are supported for SQL Server VMs. One fact to note, however, is that all SQL Server databases within a SharePoint farm need to be restored from the same point in time as the other databases. This applies to virtualization snapshot technology or storage area network (SAN)-based snapshots of SQL Server databases.