The key to a stable and high-performance virtualized SharePoint environment is using the proper architecture in the virtualization hosts. Out-of-the-box settings and slow disks might work for a test environment, but specific requirements need to be met when building the host system for proper performance to be achieved. Therefore, be sure to follow these minimum requirements when you design the virtualization host infrastructure:

• The processors must support hardware-assisted virtualization, which is available in processors that include a virtualization option. Specifically, this means processors with Intel Virtualization Technology (Intel VT) or AMD Virtualization (AMD-V) technology.

• Hardware-enforced data execution prevention (DEP) must be available and enabled.

• SharePoint guests must be deployed on a Hyper-V hypervisor or a third-party hypervisor that’s part of the Server Virtualization Validation Program.

• Sufficient memory must be allocated for the host OS. If you’re using Hyper-V, you need to reserve at least 1GB of RAM for use by the Hyper-V host. If you’re using a third-party hypervisor, check with the individual provider to determine the minimum amount of memory required.

• A dedicated NIC must be allocated for host management. This NIC must be separate from the NICs used by the VMs.

• Use multiple storage arrays or sets of disk spindles. Best practice is to allocate a dedicated storage array or set of disk spindles for the host OS, another for the guest OS, and at least two more for logs and database volumes in virtualized SQL Server sessions.

• Fixed-size or pass-through Virtual Hard Disks (VHDs) must be used. All VHDs used by SharePoint servers need to be either fixed-size or pass-through (raw) disks that are directly connected to a volume on the host storage. Pass-through disks give you the fastest performance, which is highly recommended for SharePoint servers. Fixed-size disks are faster than dynamically expanding disks, which can suffer performance hits when they’re resizing.

• A 2:1 ratio for the number of virtual processors to physical cores must be used. A virtual host that has too many allocated virtual CPUs can be overloaded and perform poorly. Therefore, you need to have a 2:1 ratio (or less) for the virtual processor to physical core ratio. For example, if your host is a 2-processor quad-core system (8 cores total), the maximum number of virtual processors that can be allocated and running at any one time is 16. If each VM is allocated 4 virtual processors, the number of running VMs is capped at 4 on that host. In addition to these technical requirements for
the virtualization host, you need to keep in mind these recommendations when you design your virtual environment:

• You should allocate a dedicated NIC for failover. If you’re using virtual host failover software such as Hyper-V Live Migration, you should use a dedicated NIC for the failover.

• You should give as much memory and as many processor cores to your virtual hosts as your budget allows. Virtual hosts with multiple multicore processors and large amounts of RAM (64GB or more) are becoming commonplace because of the virtual host software’s ability to take advantage of the additional resources and because host failover solutions require additional resources. When it comes to sizing virtualization hosts, there’s a sweet spot that balances the cost of the additional components against the need to have fewer hosts. Generally, the virtualization overhead required to run virtual servers is only 5 percent, so the cost of adding memory and processor cores is more than made up by the advantages of having those additional resources.

• You should run only the virtualization software and the virtualization role on the virtual hosts. (The two exceptions are antivirus and backup software.) Overloading a virtual host with other software or other server roles can significantly degrade guest performance. In addition, from a Windows Server licensing perspective, running any roles other than the virtualization role on a Windows server requires one additional license. However, if the host runs only virtualization host software, the host OS isn’t counted when determining the number of Windows licenses that are used as part of Microsoft’s virtualization licensing program.

• You shouldn’t install all the SharePoint roles and the SQL Server role on the same VM for performance reasons. Even small environments should use at least two VMs—one for the SQL Server database role and one for the Share-Point front-end and application roles.

Source of Information : Windows IT Pro June 2010


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