Running SQL Server on Hyper-V in Visual C#

Create Code 128C in Visual C# Running SQL Server on Hyper-V

As you can see, the parent partition is using 83 percent of the available CPU resources. If a process running in the child increases to take 40 percent of the available CPU, competition for the overtaxed CPU resources occurs. The child takes resources from the parent, reducing the resources for the parent. There isn t an overall Task Manager for the entire physical machine that shows the sum of all of the individual Task Managers. Hyper-V provides its own set of Perfmon counters to provide a view of both what is happening at the overall physical server level as well as within the Hyper-V environment. These Hyper-V counters are exposed in the parent partition (that is, physical machine). You may choose from many different categories of Hyper-V counters. Refer to the Hyper-V documentation and product team blogs to determine which counters are most useful to you. Tony Voellm s blog at http:/ /blogs.msdn.com/tvoellm/ is an excellent source of in-depth information on Hyper-V performance monitoring. Use the Hyper-V counters to make sure that the total physical CPU resources on your Hyper-V server are adequate to service all of your running virtual machines.

Hyper-V offers both legacy network adapters and synthetic network adapters. Legacy network adapters are emulated devices and as such offer lower performance than synthetic adapters, but offer greater compatibility with older operating systems. Synthetic adapters provide near-native performance and require that Integration Services be installed in the virtual machine, which is not possible in all cases. When Integration

Services is installed, it installs drivers that enable synthetic (virtual) devices to work. A legacy network driver is slower because it emulates a physical device instead of being an outright substitute like a synthetic device. Integration Services cannot be installed in Windows Server operating systems prior to Windows Server 2003 R2 Service Pack 2. For example, a SQL Server 6.5 instance running in an NT 4 virtual machine must use a legacy network adapter. The minimum number of recommended physical network adapters for a Hyper-V physical machine is two (although it is possible to run with a single network adapter). One should be reserved for use only for administering the physical machine. The other is used for the virtual machines. If there is substantial network traffic, it may be necessary to have one or more physical network adapters for each virtual machine. To ensure optimal network performance, check with your hardware vendor to ensure that you have all of the latest drivers. Network-intensive workloads use more CPU in a virtual machine than on a physical machine. For deeper technical information and best practices, see Microsoft s whitepaper Running SQL Server 2008 in a Hyper-V Environment, downloadable from http:/ /download.microsoft.com/download/d/9/4/ d948f981-926e-40fa-a026-5bfcf076d9b9/SQL2008inHyperV2008.docx.

Hyper-V does not allow memory to be overallocated. If 2 GB of memory is allocated to a virtual machine, but only 1 GB is ever actually used, the 1 GB of unused RAM is not available for use by other virtual machines. This imposes a limit on how many virtual machines can be running at any given time. The sum of the memory allocation for all running virtual machines should be 1-2 GB less than the server s physical memory. Enough memory has to be left available so that the hypervisor itself (and any antivirus software running in the parent partition) has enough RAM to avoid paging.

It is common for database applications to need accurate timestamps for data. Operating systems employ various techniques to minimize clock drift where the time on the computer diverges from the time. Multiprocessor virtual machines can introduce additional clock drift because of how processor resources are shared. By default, Hyper-V Integration Services synchronize the virtual machines with the physical machine. If you want to treat the virtual machine more like a physical machine, you can disable the time synchronization in Integration Services and instead use synchronization with an external time source or a primary domain controller (PDC) emulator.