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| Virtual Server 2005 R2 SP1 Ships |
| Jun. 25, 2007 |
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After multiple delays, the first service pack for Microsoft Virtual Server 2005 R2, Microsoft's hardware virtualization product for hosting virtual machines (VMs) on Windows Server 2003, has finally shipped. In addition to fixing many serious bugs, the service pack adds several important new features, particularly backup for live VMs. This service pack is particularly important to IT shops running production servers on Virtual Server 2005 R2, but the new backup capabilities cannot be exploited by any backup solutions currently on the market. SP1 Enhances Server Virtualization SP1 is the latest update to Virtual Server 2005 R5, Microsoft's hardware virtualization product for servers. In hardware virtualization, only the host OS (the first OS installed on the computer) is communicating directly with the hardware. All the other OSs (called guest OSs when run this way) and applications installed on these OSs run in VMs, which emulate generic resources, including the CPU, memory, disk controller, graphics adapter, and network adapter. A physical computer can run multiple VMs simultaneously. By decoupling the guest OSs and the applications running on them from dependencies on specific hardware, VMs can be created quickly and moved easily between servers. Although Microsoft has not supplied a listing of problems repaired by SP1, it fixes many serious bugs, particularly several associated with Virtual Server's virtual SCSI interface. One in particular created incompatibilities with some Linux distributions. These fixes alone make SP1 particularly important to organizations that run production VMs on Virtual Sever 2005 R2 and therefore need it to be very stable. In addition to the bug fixes, SP1 introduces a number of new features, the most interesting of which are support for new hardware-assisted virtualization and live VM backup. Hardware-Assisted Virtualization In the first half of 2006, new servers containing AMD Pacifica or Intel VT chip sets began hitting the market. While the technologies are different, both provide hardware-level support for virtualization by allowing the OS in each VM to share the CPU's most privileged "Ring 0" execution level, even though Ring 0 was originally designed to be accessed exclusively by a single OS. Although SP1 doesn't require the new Intel or AMD hardware, it enables Virtual Server 2005 R2 to exploit both technologies, which provide substantially improved performance for non-Windows guest OSs. Although the new hardware-assist also greatly accelerates installation of Windows OSs in VMs, the new hardware has little impact on Windows VMs once software called the Virtual Server Additions has been installed on the guest OS; the Additions provide accelerated performance without exploiting or benefiting from the virtualization hardware. Live Backup SP1 introduces new technology for backing up running VMs, although it will not be practical until backup software vendors exploit it. Shadow Copies Avoid Shutdowns, Agents Until SP1, customers had two options for backing up a Windows-based VM reliably. They could either shut down (or pause and save the state of) the VM and then use conventional backup software to copy the VM's virtual hard disk file (VHD) to backup media or they could install remote backup agents on each VM and perform an over-the-network backup on each just as if they were physical servers. However, both approaches have limitations. The first approach is undesirable because it takes the VM out of service for a significant amount of time, which potentially impacts users and is difficult to automate. The second approach, while nondisruptive and easy to automate, doesn't exploit the benefits of virtualization because, should the VM be damaged or destroyed, it is just as difficult and time-consuming to restore a VM to a prior known-good state as it is to do the same with a physical server. SP1 will eventually give Virtual Server 2005 R2 customers a third option: backing up each VM's VHD file while running. New APIs in Virtual Server 2005 R2 SP1 allow backup applications to control the Volume Shadow Copy Service (VSS) services on both the host and Windows-based guests (which must be running the upgraded Virtual Server Additions supplied by SP1). VSS is a Windows service that lets applications, OS services, storage devices, and backup applications work together so that clean "shadow copies" (i.e., snapshots) can be made by most storage technologies with only a brief pause to applications. When a local backup program or agent running on the host signals Virtual Server that it needs to take a snapshot of a VM, Virtual Server instructs the VM's VSS to make the OS and VSS-enabled applications running in it (such as Exchange) complete their current file system transactions and pause. The host's VSS then takes a snapshot of the VM's VHD file (which takes only a few seconds) and signals the VM to resume normal operations. The backup program can then perform a clean backup of the VHD snapshot without interfering with the live VM. Restoring an entire VM from a backup simply requires an administrator to replace the VHD file of a shut-down VM with the desired backup copy, and then restart it. Restoring individual files in a VM is also possible: the administrator copies the backed-up VHD file to a host running Virtual Server 2005 R2 SP1 and then uses a new utility installed with SP1, VHDmount.exe, to mount the VHD file to the file system, where it appears as a physical disk volume (the VM remains shut down). The administrator can then copy, rename, or replace files to any location using standard network file management tools, such as Windows Explorer. Backup Implementation Scarce Unfortunately, as of June 2007, no third-party or Microsoft backup program, including the one bundled with Windows Server 2003, supports the new backup API, and no vendor has committed to supporting it. One possible reason: native Windows virtualization support planned for Windows Server 2008 (formerly code-named Longhorn) will involve a different API. Backup software vendors are probably reluctant to invest in a technology that will quickly become deprecated. However, the next release of Microsoft's Data Protection Manager (DPM) 2007, currently in beta and scheduled for release in the second half of 2007, will fully support live VHD backups. DPM enables network backup of files from Windows file servers to tape-based or disk-based storage and can take backups many times per day, thereby reducing file restore times and the risk of lost data. Customers should also be aware of one other caveat: the new VSS support cannot perform live backups of VHDs that contain the FAT file system (instead of NTFS) or that are configured to be dynamically expandable. (Dynamically expandable disks enable VHD files to start small and grow as needed, but impose a performance penalty.) Added Guest OS Support SP1 adds support for the following additional guest OSs:
These OSs will perform adequately without special Virtual Server addition software, providing they are running on servers that have AMD Pacifica or Intel VT support enabled. Through a partnership with InnoTek, however, Microsoft has begun offering free virtual machine additions that optimize performance of Linux guest OSs running certain versions of Red Hat and Novell SUSE, and that provide decent performance on older systems that don't have virtualization hardware. A beta version of this software has been available for download for over a year, but a final release date has not been announced. There is no change in Microsoft's support policy for running Linux as a guest OS: Microsoft Customer Service and Support (formerly Product Support Services) can provide technical support for running Linux guest OSs on Virtual Server 2005 R2. Through an arrangement with partner Wipro, when Premier or Professional support customers call Microsoft with issues related to running Linux on Virtual Server, Microsoft will diagnose the problem and then transfer the case to Wipro. While Vista or Windows Server 2008 work fine as guest OSs under Virtual Server 2005 R2 SP1, Microsoft will support these only for non-production use. This is puzzling because Vista shipped six months before SP1, and Microsoft had indicated earlier that SP1 would add support for Longhorn. Resources SP1 can be downloaded from www.microsoft.com/technet/prodtechnol/eval/virtualserver/default.mspx. Hardware-assisted virtualization and Microsoft's virtualization roadmap are described in "Changes to Server Virtualization Roadmap" on page 14 of the Jan. 2006 Update. Data Protection Manager 2006 is described in "Data Protection Manager Ships" on page 10 of the Nov. 2005 Update. Beta versions of the Virtual Machine Additions for Linux can be obtained at https://connect.microsoft.com/content/content.aspx?ContentID=1475&SiteID=154. |
