The three main competitors in the Intel server virtualization space--VMware, Connectix, and SWsoft--offer unique approaches.
To help you decide which solution best suits your company's needs, Tech Update interviewed these three vendors. VMware CEO Diane Greene, SWsoft CEO Serguei Beloussov, and Michael Shaler, Connectix director of product management, described their companies' approaches to server virtualization, product positioning, and their visions of the future of virtual servers.
Approaches to server virtualization
We asked each vendor to explain why their approach to server virtualization is unique.
Vmware's Diane Greene said, "Our virtual machine software virtualizes the Intel platform so you can run multiple operating systems and applications at the same time. We do this by providing hardware-level virtualization through the use of virtual machine technology. A VMware "partition"--or virtual machine (VM)--presents a complete set of virtual Intel x86-compatible hardware to the operating system image running within the VM. This virtual hardware provides a virtual implementation of every device found on a real server--from the motherboard chipset to the CPU and memory to SCSI and IDE disk devices to ports and display devices. [And] each virtual machine is encapsulated in a file, providing the ability to move workloads from system to system seamlessly."
Greene added, "We run close to the physical hardware in two distinct ways. First, across all our products, our VMs execute most CPU instructions directly on the system processor without intervention from our virtualization layer. Second, in the case of ESX Server, we actually run the virtualization layer directly on the hardware itself, without requiring a host operating system at all. When we do this, we can "take over" the hardware and precisely control the physical resources consumed by each virtual machine down to specific levels of network bandwidth or even disk I/O access. Virtual machine technology running on top of a host OS cannot achieve this level of control."
Greene added that VMware technology provides partition isolation. "To have true performance isolation, every partition should be able to count on having access to a certain amount of system resources, including disk I/O and network bandwidth. For security isolation, a malicious user in one partition should not be able to hack through to another partition."
Michael Shaler described Connectix's Virtual Server approach as "offering" two core technological competencies: virtualization, which means to implement in software what previously existed in hardware, and binary translation, which means that we translate one instruction set to another (x86 to PowerPC, or x86 to virtualized x86 instructions) … We support a broad range of guest OSs--we can run OS/2 and NetWare with complete driver compliance on those platforms." Virtual Server can also run Linux, Windows NT, 2000, and .Net servers.
Virtual Server echoes VMware's GSX Server in that it runs guest OSs on an existing host OS, and offers a similar approach to portability. Shaler explained, "Our 'virtual hard drives' (VHDs) feature a level of portability--[which means] the ability to access and move a complete self-contained server environment wherever needed on the network--that delivers instant-on deployment and instant undo. A virtual hard drive is similar to an OS image file, but differs in that you can boot from a read-only VHD that resides on the file system and save all disk writes to a 'differencing' drive that can either be merged with the boot drive or be discarded [i.e., instant undo]."
Shaler continued, "What we mean by 'instant-on' deployment is that a VHD residing on the file system can be accessed and booted remotely for capacity-on-demand deployment of additional server resources."
Serguei Beloussov said SWsoft's Virtuozzo takes a somewhat different approach. "[Virtuozzo] virtualizes the operating system (OS) layer on Intel-based servers, creating fully-isolated virtual partitions, implementing functional, fault, namespace, and resource isolation between partitions. [This approach] produces less than 1 percent total overhead per server regardless of the number of virtual environments/partitions on that server. Our technology modifies the base kernel (right above the root OS) and creates fully-isolated virtual environments (VEs) that are instances of that same OS. Each VE can scale to 64GB RAM across 16 CPUs, and each partition can fairly and dynamically share server resources. A single kernel at the base of the server is aware of all of the applications, sites, etc., housed with each of the virtual partitions, and monitors and tracks changes in each. What's more, you can drag and drop VEs between physical servers, all from the management console."
Speaking of management, Beloussov explained, "Each of VEs is fully isolated and can be managed from a management console that enables the user to monitor VEs, applications, bandwidth, memory, I/O, and other resources levels."We asked each company to differentiate its approach to virtualization from their competitors'.
VMware's Greene said, "A very important thing is just that we've had our Intel virtual machine technology in such wide deployment for so long … By having over 1,200 customers deploy our server technology, we've been able to gain a tremendous amount of experience about what customers want and how they expect to use our products. All that experience has gone right back into our current second generation servers, and that's why we're seeing such rapid adoption. Our success in the enterprise is due in part to our rock-solid isolation capabilities--we've even had the National Security Agency perform an audit of our source code to satisfy themselves that we have true isolation among virtual machines."
Connectix's Shaler compares his company's Virtual Server to VMware's GSX Server and ESX Server products. "While GSX and Virtual Server are similar in that they are both hosted on Windows servers, there are vast differences in terms of our superior memory management and performance optimizations associated with our balanced approach to binary translation and direct execution modes. Virtual Server performs on parity with ESX and significantly out-performs GSX. ESX and Virtual Server are both highly-scalable, enterprise-class virtualization solutions that take very different approaches to solving a complex problem: we started with complete emulation and then optimized for performance, [whereas] ESX started with hardware virtualization and then optimized for a more limited range of compatibility.
"Simply put, we are a Windows-hosted solution with superior compatibility and extensibility, whereas VMware is a proprietary-hosted solution, and Virtuozzo is a pure-play Linux offering."
SWsoft's Beloussov claims Virtuozzo's approach "is different from the virtual machine (VM) technologies found in offerings from VMware and Connectix in that the technology virtualizes the OS layer. VMware's VM technology emulates the hardware layer, which creates serious overhead that increases proportionally [as] the number of VMs [increases]. If you are running five to fifteen VMs on a server, it's possible [for a server to] spend over half of its CPU cycles processing virtualization, instead of a business-critical operation.
"Virtual machine technologies do not utilize hardware well--if there are 20 VMs on a single machine and 19 are idle, the remaining one will only work with up to one CPU and 4GB of RAM. [Our] VEs can use all available CPUs and RAM on the same server, dynamically reassigning resources without rebooting the system (as with a VM).
"Another advantage [of VEs] is en-masse management of partitions through sophisticated templating technology. All applications, Web pages, and anything else housed within a VE is managed in one place, with the unique ability to mass-deploy updates and migrate partitions between physical servers with little or no downtime."
However, Beloussov conceded that VM technology does offer the advantage of running disparate OSs on the same physical machine, whereas Virtuozzo currently supports only Linux.Intel-platform server virtualization is relatively new, but all three vendors have specific ideas about where its product lines--and the technology in general--is headed.
VMware's Greene said, "We think that the server virtualization capabilities envisioned by IBM's eLiza, Sun's N1, and HP's Utility Datacenter represent the future of server-side computing. All of these require the ability to dynamically repurpose servers for new tasks, while maintaining constant service availability. They have the vision of hardware being managed as a single pool of computing resources. Due in part to their hardware independence and encapsulation capabilities, VMware virtual machines are a natural enabler for the kinds of dynamic computing environments envisioned by the major server providers. We see our virtual machines serving as key building blocks in blade, grid, utility computing, and server virtualization scenarios.
"Longer term, we think we're headed for a world in which the services that run on top of a computing infrastructure, like an e-business service or a supply chain service, will be deployed and managed completely independently of the physical components that power the service. That's Microsoft's .Net vision, and that's very exciting indeed."
Beloussov described SWSoft's roadmap: "In the short term, we will continue to improve Virtuozzo and dominate the market for Linux/Unix virtualization in the hosting space. In the next few releases, we will continue to productize Virtuozzo for the enterprise, providing more service-level and mass-management tools that make it easy to manage and deploy virtualized environments on Intel-based servers.
"In addition to an Itanium product--which should be out by next summer--we are putting a lot of development muscle behind our Windows offering--due out the second quarter of 2003--which will make us more attractive to enterprise customers. Longer term, we will release a sophisticated and integrated storage virtualization product."
And as for the future of virtualization, he said, "Server virtualization will play a pivotal role in helping enterprises, SMBs, hosting providers and other organizations fully utilize and consolidate hardware. For service providers, server virtualization will redefine the industry by providing an automated infrastructure on which to create both new channels and a wide-range of virtual hosting plans."
Shaler described the Connectix roadmap. "In the short term, we are focused on saving customers money today in the 1- to 4-way range, consolidating commodity infrastructure services such as file/print, collaboration, and domain control servers. We're very excited by the capabilities that Microsoft's .Net server brings to the table for us, and are very busy right now cultivating technology and reseller partnerships to enlarge the capabilities of Virtual Server as a virtualization platform. Connectix's open-platform approach enables the creation of value-added applications by partners.
"As we move forward to the vision of a processor area network enabled by self-healing autonomic computing, we will see more powerful, flexible, reliable solutions leveraging Virtual Server to continue to save our customers money. The datacenter of the future, enabled by server virtualization, is going to be a very exciting place to be."