Following those features are slightly less important ones such as thin provisioning, VM snapshotting and templating, automated VM backups, live storage migrations, and advanced memory management features, including page sharing, memory compression, and memory ballooning.
VMware is still the only solution that can handle live storage migrations, and only VMware vSphere and Red Hat Enterprise Virtualization can claim to offer page sharing and memory compression. However, the other features are available across the board. Thin provisioning and templating are features that make deploying large numbers of VMs trivial, and at the same time reduce the impact on storage. Advanced memory management capabilities optimize the allocation of physical memory to virtual machines.
These tools are extremely important in infrastructures running a large number of VMs per host, and a large number of VMs overall, but smaller environments may not need them straight away. While definitely important, these features do not have as direct an impact on end-users as live migrations, high availability, and load balancing, especially considering the number of smaller organizations that are planning on virtualizing their entire server farm and will experience less churn than larger infrastructures.
Further down the feature trail, we get into more rarified air -- and items like API integration, which can provide massive benefits to larger implementations. All four solutions offer some form of CLI or scripted management, ranging from VMware's mature API integration to Hyper-V's use of PowerShell to allow for scripting administrative tasks.
There's also something to be said for guest OS support. Only VMware goes as far as explicitly supporting Mac OS X Server, FreeBSD, NetWare, and Solaris. You can even run OS/2 Warp if you like. The rest stop at a few Linux distributions and Windows platforms.
The long and the short of it is that at this point in time, all of these vendors can provide enough features to consider their use in a production capacity in a wide variety of deployment sizes and types. However, VMware still has the most mature and feature-rich offering among them. You'll find a features comparison table on the next page; the article continues on the following page.
Virtualization platform licensing The licensing structures of VMware vSphere and Microsoft Hyper-V are definitely more complex than those of either Red Hat Enterprise Virtualization or Citrix XenServer. VMware offers several levels of vSphere, each with more features than the last, and all priced per physical socket. Microsoft offers Hyper-V as part of Windows Server 2008 R2, with an Enterprise license allowing for four virtual servers running the same OS on a physical server, and a Datacenter license allowing for unlimited virtual machines per physical server.
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