This series of articles provide an overview of how to plan, build and configure the common SharePoint farm across your organization.

• Part 1 – Architecture and Logical Planning
• Part 2 – Installation
• Part 3 – Development Environment
• Part 4 – Backup and Recovery Strategy
• Part 5 – Virtualization
• Part 6 – Post Deployment (final)

Virtualization

Virtualization in SharePoint farm is one of the key design factors that simplify server availability by providing number of additional servers that might not be available over physical server models, or solution become very expensive. Microsoft officially supports SharePoint farm in virtualized environment since mid 2007. The following virtualizations technologies are supported: Hyper-V, Virtual PC, Virtual Server and 3rd party providers like VMware.

One of the key factors for virtualization is that performance of virtualized farm is competitive to the physical farm. Microsoft tests shows:
- 7.2% less throughput on virtual Web roles with 8GB of RAM than a physical Web role server with 32GB of RAM;
- 4.4% slower in the page response time on the Hyper-V Web front-end than the physical server;

Virtualize SharePoint Web Role

Web front-end servers are responsible for the content rendering and have comparatively lower memory requirements and disk activity than other roles, what makes them is an ideal candidate for virtualization.

Choose disk type for Query Role

The query role is responsible for a search performed by users is a good candidate for virtualization. The disk type choice for this role depends on the size of propagated index and the rate of index propagation.
The recommendation for the large indexes and the farm with the high rate of the updated information to use a physical disk volume that is dedicated for the individual query server, rather than a virtual disk file.

Consider using Index Role on physical server

The Index server role in a SharePoint farm is often the most memory-intensive role, what makes it less ideal candidate for virtualization. Virtualized Index server role might be appropriate for development environment, small farm or farm with small content usage.
Take into account, that index can vary from 10% to 30% of the total size of the documents being indexed. For the large indexes (above 200 GB) consider using physical disk volume that is dedicated to the individual query server, rather than virtual disk.
For large farms with big amount of crawled data use physical Index server role due to large memory requirements and high disk I/O activity.

Do not virtualize Database role

SharePoint database role is the least appropriate role for virtualization in production scenarios, mainly due to the highest amount of disk I/O activity and very high memory and processor requirements. However, it is very common to see the SQL Server virtualized in test farms, quality assurance (QA) farms, and smaller SharePoint environments.

Do I need to virtualize Application role?

The decision of virtualizations the application roles, such Excel Services and InfoPath Services, depends on the roles usage. Those roles can be easily virtualized, because they are similar to Web Roles and mostly CPU intensive. When necessary, those servers can be easily moved to dedicated physical servers.

Virtualized scenario sample

The following picture demonstrates the common virtualized scenario of SharePoint Farm.

Common deployment scenarios for the SQL role in a SharePoint farm may have multiple farms, both physical and virtual, use a single database server or database cluster, further increasing the amount of resources consumed by the role. For example, in the picture above, the sample SharePoint environment illustrated maintains a two-server SQL cluster that is used by several virtual farms and one production farm.

Use proper number of CPU

Do not use more virtual CPUs than physical CPUs on the virtual host computer – this will cause performance issues, because the hypervisor software has to swap out CPU contexts.
The best performance can be realized if the number of virtual processors allocated to running guests does not exceed the number of logical processors (physical processors multiplied by the number of cores) on the host. For example, a four processor quad-core server will be able to allocate up to 16 virtual processors across its running sessions without any significant performance impact. Note that this only applies to sessions that are physically running simultaneously.

Use proper amount of RAM

Plan to allocate the memory on virtual sessions according the next rule – divide the total amount of RAM in the server by the number of logical processors (physical processors multiplied by number of cores) in the host server. This will align allocated memory along with NUMA sessions. Otherwise it will provide performance issues.
In some testing, a virtual SharePoint Web server role with an allocation of 32GB of RAM actually performed worse than a virtual server with an allocation of 8GB of RAM.

Plan to use physical drives

In virtual scenarios front-end Web servers or Query servers disk performance is not as important as it would be physicals servers of the Index role or a SQL Server database. A fixed-size virtual disk typical provides better performance than a dynamically-sized disk.
If disk speed is a high priority, consider adding physical drives to the host computer. Add new virtual hard drive and map it to an unused physical drive on the host. This configuration, called a “pass-through disk”, is likely to give the best overall disk throughput.

Consider using hardware load balancing

Hardware load balancing provides the best performance, comparing with the software load balancing. It offloads CPU and I/O pressure from the WFE’s to hardware layer thereby improving availability of resources to SharePoint. Examples of Hardware: F5 BIG IP, Citrix Netscaler, Cisco Content Switch. Software load balancing examples are Windows Network load balancing, Round Robin load balancing with DNS. It is a trade-off between cost and performance. (Additional details are here)

Be careful with snapshot feature on virtual servers

Using snapshots for the backup might cause you troubles, because SharePoint timer service might be  unsynchronized during the snapshot process, and once the snapshot is finished, errors or inconsistencies can arise. So, consider backups over the snapshots for the production environments.

Measure virtualized environment performance

After you complete your virtualized environment installation and configuration measure how fast you environment operates and optimize it to the best performance. Measure the following parameters:
1) Processor performance – “\Hyper-V Hypervisor Logical Processor(_Total)\% Total Run Time” performance monitor counter.
Results: <60% Utilization is fine, 60%-89% – caution, > 90% significant performance degradation
2) Memory performance – “\Memory\Available Mbytes” of the physical memory available to processes running on the computer, as a percentage of physical memory installed on the computer.
Results: 50% is fine, 10% and below is critical
3) Disk performance – “\Logical Disk(*)\Avg. Disk sec/Read” or “\Logical Disk(*)\Avg. Disk sec/Write” disk latency on the Hyper-V host operating system.
Results: up to 15ms is fine, 15ms-25ms is warning, >26ms critical

Mode details about virtualized performance counters can be found in this post

Refer to the following document for more details regarding virtualization: http://technet.microsoft.com/en-us/library/cc816955.aspx