- Free download
- 64-bit and multi-processor support
- PXE provisioning of virtual machines
- virtual disk re-sizing and VM snapshot facility
- official support for Linux VMs
- Windows host only
- no virtual SMP
- no support for 64-bit guest operating systems
- limited Linux support
- clunky browser-based management
First came VMWare, which recently announced free availability of its market leading server virtualisation software in the form of VMWare Server. Then Microsoft quickly followed suit with the release of Virtual Server 2005 R2 as a free download. Moreover, the company is bowing to customer pressure by offering official support for Linux virtual machines plus a new Virtual Machine Additions for Linux pack to enhance such setups.
Microsoft’s Virtual Server could, in theory, be installed onto almost any x86 Intel- or AMD-based system. However, the recommended processor is a 1GHz Pentium or above, and the more power on tap the better. At least 256MB of memory is also required, but you’re likely to need a lot more -- especially if you intend to run a large number of virtual machines, each with its own memory allocation.
There’s support for 64-bit processors and multi-processor hosts, although no virtual SMP support for guests (as on VMWare Server) and no facilities to host 64-bit virtual machines at present, either.
As you might expect, Windows needs to be installed on the host server and will need to be licensed, whereas with VMWare you have a choice of either Windows or open-source Linux hosts. Windows Server 2003 is the recommended choice here; you can use any version, including Small Business Server. Alternatively you can run the software on top of XP, although XP is only recommended for testing and development, not for production use.
Setup & ease of use
Since it was made available free of charge, there’s now only the one Enterprise version of the Virtual Server 2005 R2. We downloaded this and installed it onto a Dell PowerEdge 2850 running Windows Server 2003 R2. Fitted with a pair of dual-core Xeon processors plus 2GB of memory and a RAID 5 disk array, the PowerEdge makes for a pretty meaty configuration and is the kind of platform required to host production servers running as virtual machines.
Deployment is straightforward. You need to make sure the host system is setup as an application server (running the IIS), and then install the Virtual Server software using the setup wizard provided. The whole process only takes a few minutes, after which you can create and manage virtual machines from a Web browser. A separate ActiveX component is also provided for remote control of each of the virtual machines, which is just like having the local console in a browser window. SSL encryption can also be enabled on any or all of the connections, with user authentication managed via Active Directory.
On the downside, the browser interface takes a while to get used to and isn’t quite as slick as the custom Windows GUI employed by VMWare, especially when run remotely. However, it does the job, with options to create a new virtual machine, allocate memory (up to 1,847MB) and specify its virtual hard disk -- which can be either a virtual IDE drive (maximum size 127GB) or SCSI (up to 2TB). Unfortunately, to get full SCSI support for Linux you need the additions pack and a Virtual Server SP1 update, which was still in beta at the time of testing. A virtual network interface is also available, either on a private internal network (VM to VM) or bridged to the outside world via a host adapter.
Start a new virtual machine and it boots just like a real PC with PXE (Pre-boot eXecution Environment) support in the R2 software to enable remote provisioning if required. Otherwise you can boot from a CD-ROM (either a real one or an ISO image) and load up the guest OS that way.
The Windows installations were straightforward and the Red Hat software also worked as expected, but we had problems getting both Ubuntu and Fedora Core to work properly -- particularly the X11 graphical interface. Given that it’s a Microsoft product that wasn’t at all surprising and anyone looking to host Linux virtual machines would be better off with VMWare -- especially for anything other than the officially supported Red Hat or SUSE distributions.
On the plus side, you can now download and install the Virtual Machine Additions for Linux to enhance Linux display, disk and networking interfaces, and also help with mouse and clock synchronisation. But, unlike the Windows Additions, the software involved has to be manually configured; and if you have a 2.5 kernel, a recompile may be required.
Virtual machine performance was excellent -- due, mainly, to the Dell server with its dual-core processors. By default, CPU resources are shared equally between the operating VMs. However, you can also manually tune the setup, typically by weighting the VMs or by allocating each a fixed percentage of processing power. This is useful if you want to guarantee performance, although you can’t allocate more than one processor to a virtual machine in this release.
As with VMWare, each Virtual Server VM is held in a single file with a tool available to migrate existing physical (Windows) servers complete with all their settings and applications. You can also dynamically resize virtual disks, which is very useful, and save a VM state and reload it, which is great for testing and undoing inadvertent OS changes. Indeed, we were even able to pause and restart an operating system install this way, resuming from exactly where we left off to successfully complete the process.
Overall, Virtual Server 2005 R2 is easy to deploy, requiring no special skills over and above those of a competent server administrator. However, there’s only one choice of host (Windows) and Linux support is strictly limited -- officially to just Red Hat and SUSE. The management interface could also be improved, and if you want full cross-platform support, 64-bit guests or virtual SMP support, you'll want to look at VMWare. That said, the Microsoft package goes about its job in workmanlike manner, does what it claims, and is free -- making it well worth trying for yourself.