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Moving from Physical Machines to Virtual a Primer

September 16, 2008

The method and tools employed for physical to virtual (P2V) machine migration will vary depending on the scope of the project and number of servers involved. For a comprehensive migration of a large number of
heterogeneous servers, PlateSpin has been the gold standard for P2V management. However, VMware’s latest offering, VMware Converter 3, has gained considerable ground and is priced aggressively.

Executive Summary

Beyond making a business case for server consolidation using virtualization, the critical implementation question is: How do we get there from here? Choosing the most efficient physical to virtual (P2V) methods and tools will ensure that consolidation savings are not threatened by lost productivity. This research note includes:
» Four key considerations in choosing P2V tools.
» A review of five different P2V methods.
» Tools and a recommended course of action for each method.
The methods and tools employed will depend largely on the scope and complexity of the migration project.

Key Considerations

P2V essentially involves moving applications and an operating system from a physical x86/x64 server to a virtual machine (VM). This virtual machine is hosted with other VMs on a server such as VMware’s ESX. The operating system of the virtualization candidate is likely Microsoft Windows but can also be a Linux variant.
P2V migration is not just a simple file transfer. P2V also involves establishing an appropriate VM configuration for the migrated server and changing the OS configuration to run optimally on the virtual machine. For example, the migrated OS is configured with the right drivers and configuration files so that it boots properly on its new virtual machine.

P2V method and tool selection should include the following considerations:

1. It’s a Windows thing. Just as with a migration of an application server from one physical box to another, hardware and configuration differences between the two platforms can cause problems. This is particularly true with the Microsoft Windows migration.
Windows is notoriously finicky about changes in hardware configuration. If a migrated server OS sees new or different hardware upon startup it will look for drivers for that hardware. If the drivers aren’t present, the server won’t work properly.
2.    Consolidation Goals and Capacity Planning. The method and tools for P2V migration will depend largely on the size and scope of the virtualization project. A necessary pre-requisite for P2V is that consolidation goal setting, identification of virtualization candidates, and capacity planning has already been accomplished.
The P2V methods and tools identified below range from one-off manual processes through to complete P2V automation for large numbers of servers. These solutions also vary in cost from free to thousands of dollars. The best rout for P2V will be different for a handful of servers than for a wholesale consolidation of dozens of servers to VM host machines.
3.    Limit Interruption of Server Operation. In order to migrate a server from physical to virtual environments, it has typically been necessary to shut down the physical source server. For example, one common method is to use a boot CD on the source server that is equipped with an operating system and migration software. The server is shut down and re-booted with the CD in order for the migration to work.
In addition to the inconvenience of taking a server off line for the duration of the migration, using a boot CD can also be a problem if the source servers have not been physically centralized. For distributed servers an administrator needs to go out to each of the source servers to affect the migration.
A recent development in P2V migration tools has been the ability to migrate servers to virtual machines without bringing down the source server. This is accomplished through a method similar to live disk snap-shotting, where data blocks are copied to a virtual disk rather than file segments.
In identifying consolidation candidates, be sure to have a clear sense of the toleration for downtime of each server. This is particularly important for migration of production environment servers.
4. Consider V2V and V2P as well. In considering P2V tools it may be worthwhile to also consider the ability of a given solution to move virtual servers to physical servers (V2P) or to move a virtual server from one kind of virtual machine to another (V2V).
V2P capability could be valuable in the following scenarios:

  • A server instance is moved from a physical machine to a virtual machine. However, performance does not meet initial expectations. A short term solution is to move the server back to a physical machine.
  • A new server application is developed and tested on a virtual machine. It is time to “go live” with a production version of the application but it is decided that the production version should be hosted natively on a physical server.
  • In a V2V scenario servers running on one kind of virtual machine are migrated to a different kind of VM. So, for example, servers that were developed and tested in Microsoft Virtual Server 2005 might be migrated to VMWare machines running on an ESX Server.

Implementation & Integration

Below is a list of five possible paths to P2V migration. For each we discuss the tools used (if any) and tool vendor examples. For each we provide a recommendation as to the most appropriate situation for a given method.
1. Manual P2V Migration. A completely manual P2V migration is not much different than migrating an application from an old physical server to a new physical server. The new virtual machine is configured and the server manager installs the operating system, applications and data that are present on the old server. Configuration is done from scratch on the new server. The two servers may operate in parallel for a time then the old server is taken offline and service cuts over to the new server.
The only difference between this kind of P2V and a traditional physical server to server upgrade is that the new target server is a virtual machine. As such, it can be created, configured, and provisioned much faster than a physical machine (minutes as opposed to days), and during testing phases it can be re-created and restarted much faster should something go wrong.
Some manual migration will still likely occur even for those who use an automated tool. ServiceXen research has found that among mid-sized enterprises that have implemented virtualization, about 42% used VMware’s automation tool P2V Assistant. However, none of the implementers used an automation tool for 100% of migrations. Even those who used automated tools found that building new virtual servers from scratch necessary for some migrations.

  • Cost: The time of the server administer to install and configure the VM.
  • Recommendation: Manual migration should only be used if a few servers are involved or in specific cases where automation tools don’t work. In a green field situation where most of the VMs are new or substantially changed servers and only a few servers are actual migration candidates, manual methods may suffice. It is recommended, however, that the tools for creating and configuring the virtual machines be as automated as possible.

2.    Restore Backup Server Image to Virtual Machine. An increasingly popular method for moving servers from physical to virtual realms has been to use server backup software. A server image of a physical server is created using the backup software. A new virtual machine is created and then the backup image is restored to the virtual machine. Vendor examples supporting this method include Symantec’s BackupExec System Recovery and Acronis True Image.
This method has been made possible by advancements in backup software. Traditionally backup images are configured for the specific hardware of the backed up machine. Restores needed to go back to the same machine or to an identically configured machine. Aside from P2V issues, the need to back up to identical hardware has been a hardship for IT shops that needed to maintain identical redundant server infrastructures for fail over in business continuity planning.
Symantec, for example, killed these two troublesome birds with one stone by making Symantec Backup Exec System Recovery capable of restoring images to dissimilar hardware. With the product server managers can plan to restore downed servers to non-identical physical machines or to virtual machines. They can also use the backup-restore process to move a physical server to a virtual instance for P2V migration.

  • Cost: Approximately $1,000 per server for Symantec’s BackupExec System Recovery. Approximately $700 per server for Acronis True Image.
  • Recommendation: The cost per server maybe justifiable if P2V is only one benefit of a comprehensive server availability/recoverability plan. If the enterprise is already looking to invest in comprehensive backup software a product like Backup Exec System Recovery can prove to be a very flexible solution. VMWare, for example, can import Symantec backup images into VMWare Player for testing and development.

3.    Migration Using VMware Tools. VMware is the current market leader in x86 virtualization. To maintain this leadership against inevitable challengers such as Microsoft, VMWare has been driving development of management tools as a critical differentiator. Part of that effort has included a new P2V tool called VMWare Converter. This tool combines the capabilities of two previously released VMWare tools: VMware P2V Assistant and VMware Virtual Machine Importer – a tool for converting virtual machine formats.
VMware Converter 3 was released as a free public beta in October 2006. The final release is expected in early 2007. It is also being bundled with VMWare’s Virtual Infrastructure 3 Management Center. A key feature of VMWare Converter is the ability to create virtual servers from running Windows physical servers.
With P2V Assistant the source physical server has to be closed down. The source machine is then be rebooted with a specially configured boot CD which then creates a target virtual machine on a VMware ESX Server and copies source machines files to the target machine. VMware Converter enterprise edition puts an agent onto the running source server and does non- disruptive block by block copying rather than file copying to the target VM.
VMWare Converter can also be used to import older VMware virtual machines, as well as Microsoft Virtual Server VMs and Symantec Backup Exec System Recovery machine images.

  • Cost: As a stand-alone product, WMware Converter is a free download (though still in Beta as of this writing). It is also bundled as part of VMWare’ Virtual Infrastructure 3. This is a considerable improvement over VMware P2V Assistant which was a less effective tool and started at $2,500 for a 25 migration Starter Edition.
  • Recommendation: Enterprises investing in the latest version of VMware for virtual machine hosting in a production environment (Virtual Infrastructure 3) should look first to VMware Converter. Though currently a beta product, it may be all the enterprise needs to move production servers to the new hosted environment.

4. Migration using Microsoft’s Virtual Server 2005 Migration Toolkit. A Windows-only shop that is looking at porting Windows servers from physical machines to Windows Virtual Server 2003 instances can use Microsoft’s Virtual Server 2005 Migration Toolkit (VSMT). VSMT, a free download available from Microsoft, is intended to simplify migration of an operating system and installed applications from a physical server to a virtual server that is running Virtual Server 2005.
The toolkit can be used to create images of physical computers and then deploy the images to virtual machines running on Virtual Server 2005. The types of source computers include:

  • Windows NT 4.0 Server with Service Pack (SP) 6a, Standard and Enterprise Editions.
  • Windows 2000 Server SP 4 or later.
  • Windows 2000 Advanced Server SP 4 or later.
  • Windows Server 2003, Standard Edition and Enterprise Edition.
  • The procedures for migration can be complicated, and Microsoft recommends that VSMT be used by IT professionals and consultants that “have knowledge of the operating system that you are migrating, some scripting knowledge, and knowledge of the legacy hardware environment” of the source servers. Users should have proficiency with Dynamic Host Configuration Protocol
    (DHCP), PXE, and Windows Server 2003 Automated Deployment Services (ADS).
  • Cost: Free download from Microsoft.
  • Recommendation: VSMT is only useful for enterprises that need to move only Microsoft server instances to a Microsoft Virtual Server 2005 virtual machine. As Microsoft currently does not have a hypervisor like ESX Server or the open source Xen, this kind of P2V migration will be limited to development servers and some department-level production servers. However, one area where VSMT could be used in a production environment is in re- hosting legacy Windows NT servers on Virtual Machines when their hardware reaches end of life.

5. Migration with Third Party Tools: PlateSpin and Leostream. The two leading third party P2V tool vendors – PlateSpin and Leostream – offer solid P2V automation tools at similar price points. The major differences between the two relate to scope of the P2V project. PlateSpin is the more comprehensive automated management solution while Leostream focuses on efficient P2V conversions.
PlateSpin’s PowerConvert is integrated with another program called PowerRecon for a complete capacity planning and migration management solution. The two programs are Web applications based on IIS and .Net. PowerRecon analyzes the CPU, RAM, disk, and network I/O utilization of virtualization candidates and develops a migration strategy. This includes the development of various virtualization scenarios for the host infrastructure.
PowerRecon and PowerConvert are managed from a central server. P2V migration can be scheduled using this console. Based on the PowerRecon analysis, host VMs are created on a destination server(s) with necessary configuration changes for the OS. PowerConvert then does a block level copy of data from the source machine to the target VM.
As a comprehensive automated solution, PlateSpin can also migrate virtual servers back to physical servers (V2P) and can move virtual servers from one hosting platform to another (V2V). It also supports the migration of both Windows and Linux using the same management console.
Leostream P>V Direct 3.0 does not have the broader capacity planning and infrastructure management capabilities of PlateSpin; however, it does provide a efficient tool for fast P2V migration of Windows servers to VMware or Microsoft Virtual Server machines.
A P>V Direct Wizard installs onto the source Microsoft Windows server and Host Agent installs on the target virtual machine hosting server (e.g. VMware ESX server). A target virtual machine is created on the host and Leostream does a block by block copy of the data from the physical machine to the host. There is no requirement for a reboot of the source computer though data writing on the source is suspended during the copy process.
P>V Direct also does synchronization between virtual hard disks and real disk partitions. So a virtual machine can be updated with new data that has been written to the original physical server at any time.

  • Cost: Both products cost approximately $100 per server converted
  • Recommendation: PlateSpin is the gold standard for a comprehensive P2V (as well as V2P and V2V) management and should be the first consideration for an enterprise looking to build a responsive utility infrastructure where server instances can seamlessly move from physical to virtual realms. Both products offer advanced non-disruptive migration techniques. However, recent improvements to VMware’s P2V tools mean that the technical lead enjoyed by these products is not as great as it was even a year ago.

Summary of Methods and Recommendations

Manual Physical and Virtual Migration: Building Virtual Servers From Scratch. Manual migration should only be used if a few servers are involved or in specific cases where automation tools don’t work. In a green field situation where most of the VMs are new or substantially changed servers and only a few servers are actual migration candidates, manual methods may suffice. It is recommended, however, that the tools for creating and configuring the virtual machines be as automated as possible.
Defacto Migration: Leveraging Backup Restore From Physical Server Images to Virtual Machines. The cost per server may be justifiable as P2V is only one benefit of a comprehensive server availability/recoverability plan. If the enterprise is already looking to invest in comprehensive backup software a product like Backup Exec System Recovery can prove to be a very flexible solution. VMWare, for example, can import Symantec backup images into VMWare Player for testing and development.
Migration Using VMware Tools. ServiceXen has found that 42% of mid-range enterprises implementing virtualization for server consolidation were using VMware’s P2V Assistant. VMware recently updated their tools with the new VMware Converter. For more information, refer to the ServiceXen Advisor research note, “VMware Improves Migration with Free Converter.” Enterprises investing in the latest version of VMware for virtual machine hosting in a production environment (i.e. Virtual Infrastructure 3) should first look to this tool.
Migration using Microsoft’s VSMT. VSMT is only useful for enterprises that need to move only Microsoft server instances to a Microsoft Virtual Server 2005 virtual machine. As Microsoft currently does not have a hypervisor like ESX Server or the open source Xen, this kind of P2V migration will be limited to development servers and some department-level production servers.
Migration with Third Party Tools: PlateSpin and Leostream. PlateSpin is the gold standard for comprehensive P2V (as well as V2P and V2V) management and should be the first consideration for an enterprise looking to build a responsive utility infrastructure where server instances can seamlessly move from physical to virtual realms. Both products offer advanced non-disruptive migration techniques. However, recent improvements to VMware’s P2V tools mean that the technical lead enjoyed by these products is not as great as it was a year ago.

Bottom Line

The method and tools employed for P2V machine migration will vary depending on the scope of the project and number of servers involved. For a comprehensive migration of a large number of heterogeneous servers, PlateSpin has been the gold standard for P2V (as well as V2P) management. However, VMware’s latest offering, VMware Converter 3, has gained considerable ground and is priced aggressively.

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