Although Microsoft has made decent progress in the virtualization race, there's no doubt that the leader in enterprise virtualization is VMware. VMware has been in the virtualization business since the company released VMware Workstation 1.0 way back in 1999. In addition, VMware was the first to bring bare-metal hypervisor-based virtualization to the enterprise, with the release of VMware ESX Server in 2001. VMware has a sizable lead in the virtualization market; current market estimates show that the company holds about 75 percent of the enterprise virtualization market. In June 2011, VMware released vSphere 5 -- even further raising the bar for enterprise virtualization. In addition, vSphere 5 continues to provide the foundation for leveraging virtualization to build the private cloud (see the sidebar "vSphere and the Cloud").
ESXi Becomes the Hypervisor Standard
The core of vSphere has traditionally been VMware's ESX Server hypervisor. Eventually, VMware introduced the smaller-footprint ESXi hypervisor, which the company provided as a free product. The ESXi hypervisor essentially had the same virtualization capabilities as the larger ESX Server, but it jettisoned the service console -- replacing it with a limited character-based UI and remote management through the VMware vSphere Client. The lighter-weight ESXi hypervisor also removes ESX Server's built-in web server, which means you now have to manually download the vSphere Client.
In vSphere 5, ESXi became the preferred hypervisor in part because of its smaller size but also because it has a reduced attack vector, making it more secure. In addition, the new ESXi for vSphere 5 features a built-in firewall that lets you limit traffic by IP address and subnet. vSphere 5 continues to support the older ESX Server hypervisor. The free version of the ESXi hypervisor is now called the VMware Hypervisor. (For more information about VMware's migration from ESX to ESXi, see the VMware ESXi and ESX Info Center page.)
Streamlined vSphere Editions
VMware streamlined the editions of vSphere 5 by eliminating the Advanced edition. For vSphere 5, VMware provides the Standard, Enterprise, and Enterprise Plus editions. The migration path from vSphere 4.1 Advanced is to vSphere 5 Enterprise. Table 1 summarizes vSphere 5's editions and their main features.
All vSphere 5 editions use the ESXi hypervisor, and they all support vMotion, which provides the capability to move running virtual machines (VMs) between ESX and ESXi servers with no end-user downtime. Processor and vRAM entitlement are related to changes in the vSphere licensing scheme. (For more information about processor and vRAM entitlement, see the Licensing Changes section later in this article.)
vSphere Standard is the starting point for most medium-sized business. This edition includes support for VMs with up to eight virtual CPUs, as well as support for VMware high-availability clusters and disaster recovery.
The Enterprise edition is geared for larger businesses. It adds support for hot-add RAM and CPU to running VMs, as well as support for Storage vMotion and the Distributed Resource Scheduler (DRS). Storage vMotion lets a VM's files be moved to different storage locations with no downtime, whereas DRS provides dynamic load balancing and power management for multiple ESX and ESXi hosts.
The Enterprise Plus edition is the top of the vSphere product line. It provides all the features in the Enterprise edition, plus it adds the Distributed Switch capabilities, Host Profiles, and the new Policy Driven Storage support.
For centralized management, most organizations will also want to deploy VMware vCenter Server. vCenter Server is required to enable many of vSphere's advanced capabilities. It lets you provision, monitor, and manage VMs. Two editions of vCenter Server are available for purchase: vCenter Server Foundation and vCenter Server Standard. The vCenter Server Foundation edition lists for $1,495 and includes support for up to three vSphere hosts. The vCenter Server Standard edition lists for $4,995 and isn't limited as to the number of hosts it can manage. This edition also adds process automation through the VMware vCenter Orchestrator and multi-server insight with its vCenter Server Linked Mode.
Support for Huge VMs
One of the most important changes in vSphere 5 is its enhanced support for highly scalable VMs. VMware has always been the leader in VM scalability, and with vSphere 5 the company extends its lead.
vSphere 5 VMs can have up to 1TB of virtual RAM, which is four times the virtual RAM supported by any previous release. The Enterprise Plus edition also supports guest VMs with up to 32 virtual CPUs. Thirty-two CPUs and 1TB of RAM is enough capacity to run all but the most demanding workloads.
vSphere Storage Appliance
One of the things that has slowed vSphere's adoption in small-to-midsized businesses (SMBs) is that you need to have a SAN to take advantage of vSphere's high-availability features, such as vMotion. Many SMBs use DAS and can't afford a SAN. vSphere 5 introduces the new vSphere Storage Appliance (VSA) feature, which enables the creation of shared storage using DAS from two or three local ESX servers. Although its name implies that it's a hardware device, the VSA is actually a software feature.
VSA works by dividing the non-boot storage space of a vSphere server in half and making each server node a primary for one volume and a replica for a second volume. The storage is replicated and half of the storage is assigned to the replica. If a node fails, an election occurs between the remaining nodes and the cluster directs the failover of the data store to the secondary replica.
Policy Driven Storage
vSphere 5 Enterprise Plus offers support for Policy Driven Storage. Policy Driven Storage lets the administrator create policies that determine where VMs should be located and moved using Storage vMotion. Storage policies associate VMs, data stores, and SAN devices with storage profiles. They're designed to ensure that VMs always run on the appropriate storage location to meet service level agreements (SLAs) for performance and to accommodate the VM's space requirements. A storage profile identifies the storage characteristics that a particular VM should have.
When a VM is created, it can optionally be associated with a storage profile. The storage policy determines the appropriate storage locations that meet the profile's requirements, and the administrator is prompted for the desired appropriate location. Likewise, if a Storage vMotion process is initiated, only target storage locations that meet the profile's storage characteristics will be used.
Another storage-related enhancement in vSphere 5 Enterprise Plus is the addition of Storage DRS. vSphere uses Storage DRS to balance the placement of VM files across data stores based on I/O metrics and data store capabilities. To accomplish this, Storage DRS captures latency information regarding all the data stores in the cluster. If the latency time for a given data store is above the threshold value for a significant percentage of time over a specified period, then Storage DRS automatically invokes one or more Storage vMotion operations to rebalance the VMs in the data store cluster.
vCenter Server Linux Virtual Appliance
vSphere has always required vCenter Server to provide centralized management, provisioning, updating, and load balancing of VMware vSphere hosts. In all previous releases of vSphere, vCenter Server only supported the Windows Server OSs. In vSphere 5, vCenter Server can run from the vCenter Server Appliance (vCSA).
The vCSA is a prebuilt VM that runs SUSE Linux Enterprise Server 11 and a new Linux version of vCenter Server. The vCSA comes with an embedded version of IBM's DB2 and can support up to 50 VMs. For greater scalability, it can be configured to connect to a separate DB2 or Oracle instance. The vCSA doesn't support Microsoft SQL Server. The vCSA is initially configured using a web browser; however, after the initial configuration is complete, you can use the vSphere Client to manage it exactly like the Windows version. The vCSA supports authentication using Active Directory (AD) or Network Information Service (NIS). Notably, the current version doesn't support IPv6.
New vSphere Essentials
VMware and vSphere are clearly entrenched in the enterprise -- an approach that overlooks SMBs. Traditionally, VMware and vSphere have been too expensive and too complex. With vSphere 5, VMware aims its new vSphere Essentials Kits at the lower end of the market. VMware offers two versions of the Essentials Kit: the VMware vSphere Essentials Kit and the VMware vSphere Essentials Plus Kit.
Both vSphere Essentials Kits provide support for six CPU entitlements, 32GB of vRAM, and up to eight virtual CPUs per guest. The main difference between the two editions is that the VMware vSphere Essentials Plus Kit provides support for the High Availability, Data Recovery, and vMotion features that aren't available in the less-expensive VMware vSphere Essentials Kit. The VMware vSphere Essentials Kit lists at $495 and requires a one-year support package. The VMware vSphere Essentials Plus Kit has a list price of $4,496. For centralized management, vCenter Server for Essentials is integrated into both vSphere Essentials Kits. For more information about the vSphere Essentials Kits, see the VMware vSphere for Small Business page.
Although not a technology feature, one of the most significant changes VMware introduced with vSphere 5 was a revamped licensing model. VMware has always been known to be expensive. With vSphere 5, VMware began licensing vSphere according to a more cloud-like, pay-for-consumption model.
The new vSphere 5 licensing model is still based on processor licenses, but it removes the physical restrictions of CPU cores and RAM per server. Instead, it bases the licensing on pooled virtual memory (vRAM) usage (where vRAM is defined as the memory configured to a VM). Each physical processor CPU in a server needs to have a vSphere 5 processor license. The vRAM usage is calculated using a 365-day moving average of the high daily watermark of vRAM for all powered-on VMs. There's no automatic shutdown if the licensed limits are exceeded. However, vCenter issues an alert if the available pooled vRAM is exceeded.
Customers were quite resistant to this licensing change initially, because it resulted in higher costs -- especially in situations in which memory was overcommitted. This change made high levels of server consolidation (traditionally a very desirable factor) more expensive than in the past. In addition, the new model could penalize customers for overcommitting RAM.
VMware quickly revised the vSphere 5 licensing scheme, essentially doubling the vRAM limits so that most existing installations wouldn't need to upgrade their licenses. Although large businesses will typically take these licensing changes in stride, such changes could certainly push small customers to either hold on to vSphere 4.1 or to seriously consider Microsoft's less-expensive Hyper-V product. For more information about vSphere 5 licensing, see the VMware vSphere Pricing page.
VMware's vSphere 5 continues to raise the bar for enterprise virtualization. Although Microsoft Hyper-V is gaining traction at the low end of the market, vSphere 5 remains the undisputed leader in the enterprise space. vSphere 5 offers unmatched scalability and infrastructure automation. They say there's no such thing as a free lunch, and vSphere 5 is a good example of that. vSphere 5 offers a premium virtualization feature set, but at a premium price.