VM management tools from Microsoft, VMware, XenSource leave room for improvement

Administrative actions can be delegated to authenticated, role-defined users. Like VirtualCenter, SC-VMM keeps track of what's where in the world of Microsoft-centric virtual machines through a database that itself can be stored on a guest operating system.

SC-VMM doesn't keep in revision sync physical images of virtual machines -- Virtual Hard Disk (VHD), in Microsoft's parlance -- doesn't authenticate them and doesn't have a method of putting patches and fixes into the VHDs or production guest operating systems.

We also tested a feature that lets SC-VMM perform physical-to-virtual-machine conversion. Through this process, SC-VMM "wraps up" a working server, discovering the resources used, along with files and applications, then selects "candidate"-hosted virtual-machine locations onto which it "fits" the image as a target. However, the data used isn't long and historical. Instead, it's a snapshot of conditions, so the heuristics used may or may not successfully place the image if conditions have changed considerably.

This physical-to-virtual method makes Microsoft's overall virtual-machine experience vastly less tedious. What's missing, though, is a method to freeze the process and deliver VHDs that are capable of being certified and authenticated.

In terms of its forensics capabilities, Microsoft's SC-VMM can be rich in detail. If an entire hosted server dies, however, little can be done with MVS 2005 to discern the nature of the state of the machine for forensic analysis after a total crash. To discern how the machine exploded, one still has log analysis, crash-dumps and other tools.

XenSource XenEnterprise 4

Xen initially gained strength as a paravirtualization method that Novell popularized when it elected to include Xen in its SUSE Linux Enterprise Server editions starting in SLES 9 more than two years ago.

Our take when we reviewed Xen in SLES 9 was that it wasn't quite ready for more than experimental use. We found then that Xen virtual machines were difficult to build, spawn, manage and control.

The older, Version 3 releases of Xen's paravirtualization method used a hosted operating system, whose kernel has been modified to virtualization. Xen-aware guest operating systems then were loaded atop the modified kernel/host operating system. Guest operating-system instances didn't recreate all the components (peripheral drivers, GUIs and other CPU-intensive chores), thus in theory enhancing the efficiency of guest operating systems within the Xen construct.

Xen has rapidly matured, however, and was included in Red Hat Enterprise Linux 5 shipped earlier this year, when we found it to be far stronger. Many of our objections were assuaged by its improved installation, configuration and management behavior. XenSource was snapped up by Citrix in August for a half billion dollars, coincidentally, the day after VMware's successful IPO.

The Xen project started at a university, and its appeal grew -- especially as a proof of concept for paravirtualization. XenSource, aided by investments from Intel and others, developed a commercial layer for Xen's comparatively unfriendly foundational components and aided in additional core open source Xen development (along with many others). The result was that XenSource's commercial layer, on top of rapidly evolving Xen core-virtualization components, brought features that could compete with VMware's and with what Microsoft had done with their Connectix-acquisition components for servers.

The newly released XenEnterprise 4 uses a 64-bit hypervisor and hosts Xen-aware and -compatible guests (including several versions of Linux and Solaris, as well as older, current and soon-to-be-released Windows 2008 Server editions). Microsoft and numerous Linux-distribution makers have announced or have delivered Xen-aware server and client operating-system distributions as well.

Like VMware ESX, whose list of add-ons and add-ins is huge, XenEnterprise offers the giant add-on XenCenter, an application that manages servers and pools of virtual machines. XenSource recently announced that XenCenter is now shipping part of its base offering.

Unix/Linux-savvy administrators will find much to like once the administrative options are understood. The documentation is nearly bereft of usable examples for typical virtualization scenarios, but that didn't stop us from a positive virtualization experience using it on top of SUSE SLES 10 in our tests.

We created resource pools that could be managed easily, though we were dismayed to find that many features required brittle conditions, such as homogeneous guest operating-system virtual machines, to use the control features we desired.

Making new virtual machines from physical servers is fairly easy, but there's no easy method of moving open source virtual machines to XenSource virtual machines. It's as if the machines have to be deprogrammed back to physical entities to be converted from physical servers to virtual ones and relaunched into XenEnterprise. This backward-compatibility issue means that migrations of older Xen installations into XenEnterprise will take lots of work. XenCenter doesn't offer any automation for the process yet. Moving XenSource Xen 3.0 to Xen 4.0 also required an interim step to convert to Xen 3.1. A system could be migrated this way in less than an hour in downtime.

XenCenter has a usable, Java-based GUI for doing such basic things as building a virtual machine from a physical candidate server. Much tuning, however, can be done only by using CLI tool selections, which aren't well reflected in the GUI. In fact, all three vendors have CLI or powershell commands that can be used to sculpt infrastructure and actions in a way that the GUIs can't. Of the three, XenSource's GUI is the least satisfying in this respect: We regularly had to refer to command-line options to do such things as connect to enable Xen's virtual Ethernet switch or to connect guests to the host hypervisor's network resources.

Revision synchronization, image authentication, audit and tracking, patch and fix control, as well as user role definitions and policies -- all outlined as the areas we believe need to be addressed by a virtual-machine management suite -- are lacking in XenSource's XenCenter. It's all new, and such organizations as LeoStream are partnering with XenSource to bring additional functionality. Of the three management schemes tested, XenSource's faces the most maturation but has moved forward by leaps and bounds on the back of open source components now migrating, as VMware's once did, into the commercial realm.

Final trends

Across the board, we've found that the base products tested have come a long way in terms of their setting up and deploying virtual-machine instances. The overarching trend in base virtual-machine products is to add functions as modular options. Included in those options are some management wares. As a group, these vendors would argue their comprehensiveness, but we found that most were lacking in key management features in the areas of application availability, backup procedures, security and authentication, approaches to image management and image-building resources, patch and revision synchronization, and auditing hosted operating systems.

While each of these management tasks may be on the to-do list for all these virtual-machine platform vendors, we don't expect that building applications that address them is an easy venture. Our next round of testing will examine whether there are third-party virtual-machine management products available that can indeed tackle these issues.

Henderson is principal researcher for ExtremeLabs of Indianapolis. He can be reached at thenderson@extremelabs.com.

Henderson is also a member of the Network World Lab Alliance, a cooperative of the premier reviewers in the network industry, each bringing to bear years of practical experience on every review. For more Lab Alliance information, including what it takes to become a member, go to www.networkworld.com/alliance.