Virtualizing SharePoint Components : Virtualization of SharePoint Roles

Virtualization requirements vary by server role. It is subsequently important when designing that you understand the individual requirements of each role.

Virtualization of the Web Role

The best candidate for virtualization is the SharePoint server that has the web role, which means it runs Microsoft IIS and handles all web requests sent to SharePoint. Table 1 shows resource guidelines for virtualized SharePoint servers that have the web and other roles.

Table 1. SharePoint Server Role Resource Guidelines

Roles	Virtual Processors	Minimum RAM	Recommended RAM
Web role only	2	6GB	8GB+
Service application role only	2	6GB	8GB+
Search role only	4	8GB	10GB+
Combined web, service application, and search roles	4	10GB	12GB+
Database role	4	8GB	12GB+

As you can see in Table 1, a SharePoint server that holds only the web role (otherwise known as the web server) should be allocated at least two virtual processors and a minimum of 6GB of RAM (preferably at least 8GB of RAM), along with a single VHD for the OS. If a web server needs to handle more web traffic, you can simply allocate additional web servers that have the same specifications. The size of the host OS disk should be at least 12GB plus three times the total amount of memory allocated to the VM, but it’s good practice to size this volume larger (typically around 50GB to 100GB) to allow the host OS to grow in size.

Virtualization of the Application Roles

The next likely candidates for virtualization include the SharePoint server with one or more service application roles (otherwise known as the application server). Application servers can include various service applications, such as Access Services, PerformancePoint Services, and the Managed Metadata Service. For purposes of design, this excludes the search services, which are technically service applications, but for architectural purposes are usually classified as part of a different server role.

As Table 12.1 shows, the typical virtualized application server consists of a VM with two virtual processors and a minimum of 6GB of RAM allocated to it. It needs a single VHD that’s presized in the 50GB to 100GB range for the guest OS. Note that these numbers can vary, depending on how many service applications are installed on a single machine and how many people use the applications.

In smaller organizations, the application role and the web role are often combined onto a single SharePoint server. Combining the roles will increase the memory and processor requirements of the guest session.

Virtualization of the Search Role

Third in line for virtualization is the SharePoint server or servers that hold the search role (otherwise known as the search server), which provides SharePoint’s indexing and querying functionality. SharePoint 2010 doesn’t have the same single-index restrictions that SharePoint 2007 did, which makes this role more scalable and allows for more distributed deployment models.

The typical virtualized search server consists of a VM with four virtual processors and 8GB of RAM allocated to it (see Table 12.1), assuming that SharePoint 2010’s out-of-box search functionality is being used. If FAST Search Server 2010 is used, the RAM requirements will be in the 12GB to 16GB range. Like the application server numbers, the search server numbers can vary, depending on how many items are being indexed and how heavy the search requirements are.

The search server needs a single VHD that’s presized in the 50GB to 100GB range for the guest OS and another VHD for the index and query corpus. The size of this VHD will vary, depending on how much full text is indexed from various sources.

The crawler component is used by SharePoint to crawl documents for search purposes. Multiple crawl components can be created on different servers for redundancy.

In smaller organizations, the search role is often combined with the web role. Combining these roles can increase the memory and processor requirements of the guest session.

Virtualization of a Server with All Three Roles

Many organizations combine the web, application, and search roles on a single virtualized SharePoint server. This is often the case in smaller organizations that want to deploy SharePoint across two guest sessions to be highly available but have a smaller number of guests.

Although combining the three roles results in additional load on an individual server session, many of the same processor and memory guidelines that apply to a dedicated web role server apply to a combined server, as Table 12.1 shows.

The typical virtual web/query/search server role system consists of a VM with four virtual processors and 10GB to 16GB of RAM allocated to it, depending on how many users the system will support. It has a single VHD presized in the 50GB to 100GB range for the guest OS and another VHD for the index and query corpus.

SharePoint administrators familiar with SharePoint 2007 might be dismayed at the memory requirements of SharePoint 2010, but the fact is that SharePoint 2010 requires much more memory than earlier versions. RAM requirements can be lessened, however, by turning off nonessential service applications. In general, to reduce the overall requirements of the SharePoint servers, it is recommended to turn on only those service applications required by the business.

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.