We’ve discussed Live Migration, and in addition, a number of ways that Hyper-V in Windows Server 2012 R2 accelerates that process, using advanced technologies such as Live Migration Compression, and Live Migration over SMB. We’ve also discussed the flexibility that storing your virtual disks on SMB shares brings, along with being able to move the virtual disks of running virtual machines, without taking the VM down, using Storage Live Migration. There is however, one additional type of Live Migration, that takes the best of all of the key capabilities above, and combines them in such a way as to drive the migration flexibility to its highest, and that is Shared Nothing Live Migration. Shared Nothing Live Migration allows the IT administrator to move a running virtual machine, and its virtual disk(s), from one location to another, simultaneously, with no downtime. This unlocks scenarios such as VM migration from:
Standalone Host with Local Storage to Standalone Host with Local Storage Standalone Host with Local Storage to Clustered Host with SAN Storage
Clustered Host with SAN Storage to a different Cluster with alternative SAN Storage
These are just some of the flexible migration options that administrators gain through utilizing Shared Nothing live Migration.
There are a number of steps involved in the Shared Nothing Live Migration process. Firstly, when you perform a live migration of a virtual machine between two computers that do not share an infrastructure, the source server creates a connection with the destination server. This connection transfers the virtual
machine configuration data to the destination server. A skeleton virtual machine is set up on the destination server and memory is allocated to the destination virtual machine
Figure 36 – Initializing a Shared Nothing Live Migration
Once the configuration data has been successfully transmitted, the disk contents are transmitted.
Figure 37 – Shared Nothing Live Migration – Disk contents transferred.
During this process, reads and writes are still going to the source virtual hard disk. After the initial disk copy is complete, disk writes are mirrored to both the source and destination virtual hard disks while outstanding disk changes are replicated.
Figure 38 – Shared Nothing Live Migration – Writes are mirrored
After the source and destination virtual hard disks are completely synchronized, the virtual machine live migration is initiated, following the same process that is used for live migration with shared storage.
Figure 39 – Shared Nothing Live Migration – Writes are mirrored
Once the live migration is complete and the virtual machine is successfully running on the destination server, the files on the source server are deleted.
Figure 40 – Shared Nothing Live Migration – Writes are mirrored
Cross-Version Live Migration
In previous releases of Windows Server, to move to the next version of the platform incurred downtime for key workloads, as the virtual machines were exported from old, and imported to new. With Windows Server 2012 R2 Hyper-V however, customers can upgrade from Windows Server 2012 Hyper-V with no virtual machine downtime, enabling more seamless and efficient migration of those key workloads. Note, it’s important to call out that a down-level migration is not supported.
Cross-Version Live Migration allows migration between both standalone, and clustered hosts, and the process can be fully automated using PowerShell.
Requirements
To take advantage of the discussed Live Migration capabilities, you will require the following: Windows Server 2012 R2 with Hyper-V or Hyper-V Server 2012 R2
Two or more Hyper-V hosts that support hardware virtualization, and use processors from the same manufacturer (for example, all AMD or all Intel).
Hyper-V hosts that are part of the same Active Directory domain.
Virtual machines configured to use virtual hard disks or virtual Fibre Channel disks A private network for live migration network traffic.
Live Migration over SMB with SMB Direct requires specific RDMA-capable hardware. Live migration in a cluster requires the following:
The Windows Failover Clustering feature enabled and configured. CSV storage in the cluster enabled.
Live migration by using SMB shared storage requires the following:
All files on a virtual machine (such as virtual hard disks, snapshots, and configuration) stored on a SMB 3.0 share.
Permissions on the SMB share configured to grant access to the computer accounts of all Hyper-V hosts. Live migration with no shared infrastructure has no additional requirements.
Why This Matters
Live migration, which was first introduced with Windows Server 2008 R2, was a valuable improvement for cloud management, giving organizations the ability to move virtual machines without shutting them down. As an organization’s customer base grows, however, managing the cloud environment becomes more challenging because effective resource use requires administrators to move virtual machines within a cluster and between clusters more frequently.
With the live migration improvements in Windows Server 2012 R2 Hyper-V, organizations can now not only perform live migrations, but also move many virtual machines, and their storage, quickly and without downtime, between clusters and now even to servers that do not share storage. These improvements significantly increase the flexibility of virtual machine placement by providing truly dynamic mobility of virtual machines across a datacenter. These improvements also increase administrator efficiency and eliminate the user downtime that was previously incurred for migrations across cluster boundaries. In addition to saving time because migration speed is faster, you also save time because you can perform multiple simultaneous live migrations.
In addition, the ability to harness the live migration capabilities for moving workloads onto a newer, more feature rich platform, ensures that customers can embrace the new features without incurring downtime for those key workloads and applications.