VMware vSphere ESXi 5
VMware is an old hand in the virtualisation arena, so taking a peek at its products on the web can leave your head spinning, as there's such a wide range of applications. One trap that the unwary can fall into is that some of the features described are not available on the standard product; they require additional purchases to plug in the additional functionality that you may require.
For many, vSphere ESXi is the cream of the crop, and the other vendors are simply playing catch-up. While it is true that VMware has a product for every scenario, some of the other vendors' products can be a perfect fit in terms of features suiting a particular infrastructure and scenario.
VMware is not quite as easy to set up as XenServer, for example, but it is still relatively quick and painless. The resultant interface on the host server is pure Linux CLI, and to facilitate the remote management of the host, a vSphere Client must be installed on a Windows PC as a minimum.
The client interface is clean and simple to navigate, so setting up and managing VMs is also a simple proposition. However, to ensure full management of a large-scale VMware virtual infrastructure, vCenter Server must be installed, which involves an additional cost. VCenter is a one-stop management tool, and the only tool you will need. It effortlessly manages tasks such as VM migration, load balancing and high availability, to name a few.
As previously mentioned, VMware is feature rich, but aspects such as fault tolerance are only available on Enterprise Editions and above. Disaster recovery requires the Site Recovery Manager plug-in, and virtual distributed switching requires vSphere Enterprise Plus.
For the high-availability requirements of large-scale enterprise, the VMware advanced storage management component, VMFS, is a cluster file system that leverages shared storage to allow for multiple vSphere hosts to read and write to the same storage concurrently. It provides live migration of running virtual machines from one physical server to another, automatic restart of a failed virtual machine on a separate physical server and clustering virtual machines across different physical servers.
For reliability of the platform, driver hardening is maintained as a collaborative exercise with hardware vendors, where the Microsoft and Citrix products rely on generic Windows or Linux drivers.
VSphere is the leader in terms of ultimate scalability; each host can sport up to 160 logical CPUs, 2TB of RAM and an impressive 2048 vCPUs, all shared amongst a maximum of 512 active VMs per host. The specs of individual VMs are equally impressive, with 32 vCPUs and up to 1TB of RAM. A cluster can consist of 32 nodes, with a total of 3000 VMs.
The ability to discretely manage these components for each unique VM is the true strength of VMware. The lack of reliance on a base operating system to translate and interface eliminates the I/O bottlenecks experienced by the other two products.