SQL Server 2012 : Running SQL Server in A Virtual Environment - COMMON VIRTUALIZATION PRODUCTS

If you search for virtualization products using your favorite search engine, you’ll get dozens of results for different products, and many opinions about which is best. While it’s true that the virtualization marketplace is crowded, there are still only a handful of vendors that offer production-ready server virtualization products. Developers, testers, and DBAs may already be familiar with a wider range of virtualization products, such as Oracle’s Virtual Box and VMware Workstation, but VMware and increasingly Microsoft have the lion’s share of the virtualized data center marketplace. This section looks at the primary server virtualization products available, and some of the virtualization support that hardware vendors have built into their products in recent years.

VMware

Regardless of what any other virtualization vendor’s marketing department may tell you, in my experience more businesses currently use VMware for their server virtualization platforms than any other. In my view, the main reason for this is because for a long time, VMware was almost the only vendor selling production grade virtualization software, and they also created the features that today, we expect every virtualization vendor to provide by default.

VMware’s current server virtualization product set, vSphere, consists of two components: the VMware vSphere Hypervisor, also known as ESXi, and the enterprise virtual environment management platform, vSphere.

VMware’s basic hypervisor software is available free of charge, even for production environments, and it supports running and managing a reasonable number of virtual servers on it — not bad for a free product. However, its feature set and manageability are quite limited when compared to capabilities of the VMware tools designed for the enterprise; for example, it supports only 32GB of memory in the physical host server. Nonetheless, for smaller environments or those new to virtualization, this product is often sufficient and can significantly reduce the deployment costs associated with VMware’s larger vSphere product.

To provide an enterprise-scale and feature-rich virtualization solution, VMware couples its hypervisor with the vSphere management platform. This not only provides significantly more management and reporting functionality, but also increases scalability and availability. The other major difference is that groups of physical host servers running the VMware hypervisor are managed collectively, blurring the boundaries between individual server resources and a cluster of host servers as VMware refers to it.

While production environments can be deployed using just VMware’s hypervisor, most of the businesses I work with have invested in the vSphere infrastructure to get the fuller feature set not available in the standalone hypervisor. The software is often expensive and it requires a strong commitment to virtualization, but it has been successful enough to make VMware the size of company it is today. That said, however, Microsoft is offering ever-increasing levels of virtualization functionality in the Windows operating system, and VMware will be forced at some point to reconsider the cost models and feature sets of its products.

Microsoft Hyper-V

Until very recently most of us probably didn’t think of Microsoft as a virtualization software vendor although they have in fact produced desktop virtualization software, such as VirtualPC and Virtual Server, for a number of years now. Sadly for Microsoft, my experience showed they were the kind of products that were loved by those who used them but unknown to everyone else.

First released as a role within Windows Server 2008, Hyper-V was intended to bring Microsoft’s new server virtualization capabilities to the massive Windows Server marketplace. This was an excellent product marketing decision, as anyone new to and curious about server virtualization now had the technology bought and paid for in their server operating system. No longer would they have to research, select, and download a product before installing it — more often than not on a dedicated physical server.

Hyper-V is more than just a software feature which gets installed within Windows though, it’s a component which sits deep within the operating system itself, and in some areas is closer to the physical hardware than Windows itself is once Hyper-V is enabled. It’s this low-level code that allows Hyper-V to schedule all of the different CPU requests its virtual servers make and allocate them CPU time so they can run.

Not all of the reaction to Hyper-V’s initial release was good for Microsoft though. The first version suffered from the usual inadequacies of v1.0 software we’ve become used to. In fact, it wouldn’t be unfair to say that the version that shipped with Windows Server 2008 was unsuitable for most production workloads. However, progress was made in making people aware that Microsoft was entering the server virtualization market.

Significant improvements were made to Hyper-V in Windows Server 2008 R2 and again with Service Pack 1. Live migration, dynamic storage, Dynamic Memory, and enhanced processor feature support made deploying Hyper-V in a busy production environment a reality. It is likely that many of the people who have chosen to adopt Hyper-V have done so because of Microsoft’s dominance and reputation with other applications, along with the pricing model.

In the same way that VMware offers a hypervisor product and an enterprise management platform, vSphere, so does Microsoft. System Center Virtual Machine Manager is a suite of management tools designed to manage large Hyper-V environments, as well as deploy, orchestrate, and monitor private clouds. Known sometimes as just VMM, it’s not as widely adopted as vSphere, but I suspect that will change as Hyper-V is adopted by more and more enterprise-scale customers. System Centre Virtual Machine Manager 2012 has been released with many private cloud management capabilities built into it and will be core to Microsoft’s server products strategy over the next few years.

Windows Server 2012 enhances Hyper-V’s capabilities with a compelling update of the feature. Its virtual servers will support up to 32 virtual CPUs and 1TB of memory each, while support for replication of virtual servers will offer new high availability capabilities.

Xen

Of the three server virtualization products covered in this section, XEN is undoubtedly the rarest and least widely adopted. Xen was the output of a research project by the University of Cambridge in the early 2000s, and its legacy was an open-source hypervisor. Although the open-source version still exists, a number of commercial versions are also available. Citrix Systems now owns and sells a commercial version of it known as XenServer, while the technology has also been adopted by vendors such as Sun and Oracle. Of more interest, however, is its adoption by a number of cloud service providers such as Amazon and Rackspace, demonstrating that cloud technology does not differ fundamentally from on-premise technology.

Hardware Support for Virtualization

While we can very easily see and interact with the virtualization software we install on our servers, what we can’t see is that the CPUs inside our servers now have components built into them to assist with virtualization. In the same way that CPUs had specific logic and components added to them to support floating-point and multimedia operations, they now have similar features built into them to help make virtualization software run faster. For example, Intel’s Extended Page Tables feature provides support for second-level address translation (SLAT). SLAT helps optimize the translation of a virtual server’s memory addresses to physical server memory addresses through the use of cached lookup tables.

Both AMD and Intel provide these features but with different names. AMD’s CPUs have feature sets called AMD-V and Rapid Virtualization Indexing (RVI) now built-in, while Intel’s CPUs have built-in features called VT-x and EPT. Although it isn’t necessary to know the specific roles of these components, a SQL Server professional should understand that the latest generations of virtualization software work only on server’s with these CPU features available. However, that shouldn’t be a problem, as I haven’t seen a server for a few years now that doesn’t have them built-in.