Mastering VMware vSphere 6. Marshall Nick

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      VMware vSphere Compared to Hyper-V and XenServer

      It’s not possible to compare some virtualization solutions to others because they are fundamentally different in approach and purpose. Such is the case with VMware ESXi and some of the other virtualization solutions on the market.

      To make accurate comparisons between vSphere and others, you must include only Type 1 (“bare-metal”) virtualization solutions. This would include ESXi, of course, Microsoft Hyper-V and Citrix XenServer. It would not include products such as VMware Server and Microsoft Virtual Server, both of which are Type 2 (“hosted”) virtualization products. Even within the Type 1 hypervisors, there are architectural differences that make direct comparisons difficult.

      For example, both Microsoft Hyper-V and Citrix XenServer route all the VM I/O through the “parent partition” or “dom0.” This typically provides greater hardware compatibility with a wider range of products. In the case of Hyper-V, for example, as soon as Windows Server 2012 – the general-purpose operating system running in the parent partition – supports a particular type of hardware, Hyper-V supports it also. Hyper-V “piggybacks” on Windows’ hardware drivers and the I/O stack. The same can be said for XenServer, although its “dom0” runs Linux and not Windows.

      VMware ESXi, on the other hand, handles I/O within the hypervisor itself. This typically provides greater throughput and lower overhead at the expense of slightly more limited hardware compatibility. To add more hardware support or updated drivers, the hypervisor must be updated because the I/O stack and device drivers are in the hypervisor.

      This architectural difference is fundamental, and nowhere is it more greatly demonstrated than in ESXi, which has a small footprint yet provides a full-featured virtualization solution. Both Citrix XenServer and Microsoft Hyper-V require a full installation of a general-purpose operating system (Windows Server 2012 for Hyper-V, Linux for XenServer) in the parent partition/dom0 in order to operate.

      In the end, each of the virtualization products has its own set of advantages and disadvantages, and large organizations may end up using multiple products. For example, VMware vSphere might be best suited in the large corporate datacenter, whereas Microsoft Hyper-V or Citrix XenServer might be acceptable for test, development, or branch office deployment. Organizations that don’t require VMware vSphere’s advanced features like vSphere DRS, vSphere FT, or Storage vMotion may also find that Microsoft Hyper-V or Citrix XenServer is a better fit for their needs.

      Vsphere or Vsphere With Operations Management?

      VMware sells “standalone” vSphere in one of two ways: as vSphere, with all the various kits and editions, and as vSphere with Operations Management. vSphere with Operations Management is the same as vSphere but adds the vRealize Operations Management product. In this section, we are focused on standalone vSphere only, but keep in mind that vSphere with Operations Management would be licensed and packaged in much the same way.

      No More vRAM and No vCPU Limits

      If you’ve been around the VMware vSphere world for a while, you might recall that VMware introduced the idea of vRAM – the amount of RAM configured for a VM – as a licensing constraint with the release of vSphere 5.0. As of vSphere 5.1, and continuing into vSphere 6.0, VMware no longer uses vRAM entitlements as a licensing mechanism. VMware has removed any licensing limits on the number of vCPUs that can be assigned to a VM.