This is the second part in a series about choosing hypervisors to virtualize Exchange. Read part one here.
Virtualizing Exchange can greatly benefit enterprises. It can reduce reliance on hardware and cut data center operating costs, among other advantages. But those benefits vary according to company size and hypervisor use. Let's take a closer look at some features of the three main players -- VMware vSphere, Citirx XenServer and Microsoft Hyper-V -- and how each hypervisor could work within your enterprise.
In small to medium-sized deployments, there is little functional difference between top offerings. Distinctions are sharper when building large, high-performance and highly available virtualization infrastructures. Because of their high-end scalability features, vSphere and Hyper-V make more sense in those situations.
Beyond cost and deployment scale, consider other criteria when contemplating platform options:
- Reputation. Determine how important it is to select a product considered a market leader or one that comes from a favorite vendor.
- Support. Assess how well a vendor supports its products. You don't want to be left on your own.
- Internal skill sets. Figure out if the skills within your organization align to a particular virtualization platform.
- Use case. If your organization doesn't require all of the high-end functionality in the VMware and Microsoft products, does XenServer become more attractive?
From a specification point of view, there are metrics worth considering when selecting a hypervisor (Table 1). Look at the virtualization features your version of Exchange supports. Check to see how much you intend to scale the environment over the next five years and how much money you have available to spend.
It's tempting to think it makes more sense to use Microsoft's Hyper-V to do the job as you consider whether to virtualize Exchange, but that's not necessarily the case. Exchange will virtualize well on almost any hypervisor as long as the underlying platform is designed well. Since the chosen hypervisor is only one part of the equation, you need to see the entire landscape. That means looking at hosts, storage, networking and the hypervisor to see how well they'll work together.
You can leverage some compelling licensing and platform unification by going the Hyper-V route to virtualize Exchange. From a technical perspective, you will not go wrong virtualizing Exchange on vSphere or XenServer.
When it comes to system performance, the hardware, storage infrastructure, networking/storage interconnects and other virtual workloads in the same virtualized cluster all play a part. Discuss which platform scales best for your organization's needs as they change over time.
Some critics insist Hyper-V isn't a valid deployment option because it doesn't scale the way vSphere can. Others argue Microsoft already provides services to hundreds of thousands of users daily based on systems running Hyper-V.
Special considerations when virtualizing Exchange
Depending on the version of Exchange you're using, there are a number of variables to take into account to ensure Microsoft supports any environment you build. Some of these considerations will dictate which hypervisor features and type of storage configurations you use.
Exchange 2007. Exchange Server 2007 is supported in production using hardware virtualization, but only when the chosen hypervisor is on the SVVP list. Exchange guests must run Exchange 2007 SP1 or higher, and the Unified Messaging server role cannot be virtualized.
Make sure the storage Exchange guests use block-level storage for Exchange data (databases, transaction logs, queues). Exchange doesn't support certain technologies such as network-attached storage (NAS).
Exchange does not support dynamically expanding virtual disks, and you shouldn't snapshot data disks or VMs within the hypervisor. To remain operationally supported, you shouldn't install software in the Exchange virtual guests other than antivirus, backup or virtualization management tools. If you plan to use cluster continuous replication (CCR) and single copy clusters (SCC), you can only do so when the native hypervisor high availability is not used.
Exchange 2010. For Exchange 2010 RTM, the support policy for virtualization is similar to the policy for Exchange 2007. But with Exchange 2010 SP1, Microsoft's support stance changed so all Exchange 2010 server roles, including Unified Messaging, are supported as a guest. Database availability groups (DAGs) can be used in conjunction with hypervisor high availability features; this can happen as long as the VMs are configured to shut down and cold boot or as long as an online migration (such as live migration or VMware vMotion) is used.
Exchange 2013. The virtualization support stance for Exchange 2013 is almost identical to Exchange 2010 SP1. To dive deeper, Microsoft's TechNet has detailed notes on the supported virtualization configurations.
The best advice is to do your own research; don't let those with strong opinions sway you toward a product they prefer if it might not be right for the job. Find out how your requirements, skill sets and budget align with the available products.
Evaluate each possible hypervisor and the underlying architecture so you select a platform that will meet your organization's needs to virtualize Exchange in a cost-effective and efficient way.
About the author
Andy Grogan is a multiple recipient of the Microsoft Exchange MVP award (2009-2013). He is based in the U.K. and has worked in the IT industry for the last 16 years, primarily with Microsoft, HP and IBM technologies. His main passion is Exchange Server, but he also specializes in Active Directory, SQL Server, storage solutions, technology strategy and technical leadership in large-scale enterprises. He currently works for a large county council in Surrey as its technical delivery manager and supports 15,000 customers on more than 240 sites. Visit Andy's website, telnetport25.com.
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