What’s New in Windows 8 for Hyper-V Based Cloud Computing (Part 7) – Hyper-V Continuous-Availability Scenarios

If you would like to read the other parts in this article series please go to:

Continuous-Availability with Windows Server 8 and Failover Clustering

Continuous-availability is achieved by building a system where neither a hardware or software component is a single point of failure. In addition, it must support transparent failover for server applications without data loss. Large institutions with one or more mission-critical applications have implemented these solutions in the past with Windows Server failover clustering, and additional 3rd party software or hardware to address geographical replication and consistency issues. Smaller organizations with limited IT staff and skills may have found a challenge in the implementation and maintenance of failover clustering for even basic deployments. The good news is that Windows Server 8 (officially renamed Windows Server 2012) continuously-available solution deployment and management is greatly simplified, and enhanced with new hardware support, functionality, and administrative features (including a new Server Manager with remote, multi-server management abilities) that allows it to be the cornerstone for a wide range of scenarios.

For example, mission-critical applications can now be hosted within the same failover cluster as lower priority applications without worrying about resource contention. With the new virtual machine priority functionality, Windows Server 8 supports the shut down of low priority virtual machines to free up resources for higher priority virtual machines to start when moving them around a cluster, whether as a result of a failover or maintenance event. Low priority virtual machines come back online when resources become available again.

Enhanced failover placement now takes into account virtual machine memory and NUMA resource requirements to determine the best Hyper-V server suited to host a virtual machine. These resource requirements are evaluated for each virtual machine that is placed on a host.

Live Migration is enhanced to allow concurrent virtual machine migrations, and the Failover Cluster Manager console provides the ability to multi-select virtual machines and queue them for Live Migration. Failover Cluster Manager now also provides the ability to query virtual machines by many different characteristics (e.g., priority, state, and so on), and you can save queries so that you do not have to recreate them later.

Another distinguishing feature is Automated Node Draining which provides a single-click operation that leverages Live Migration to dynamically move all virtual machines running on a cluster node to other cluster nodes. This feature, originally only provided with System Center Virtual Machine Manager to place a host in maintenance mode, supports maintaining the availability of applications during an administrative event such as cluster node updating.

Windows Server 8 also incorporates Cluster-Aware Updating (CAU) as an integral part of the Failover Clustering management experience. CAU is completely automated and works seamlessly with an existing Windows Update Agent (WUA) and Windows Server Update Services (WSUS) infrastructures. CAU also comes with an extensible architecture that supports new plug-in development to orchestrate node-updating through custom software installers, BIOS updating tools, network interface cards (NIC), or host bus adapter (HBA) updating tools. The CAU process occurs across all nodes in a cluster in a cluster-aware manner including the scan and download of updates in parallel across multiple cluster nodes, draining workloads from cluster nodes, and putting nodes in maintenance mode. Cluster node updates are performed on a single node at a time and roll through all cluster nodes. Multiple scan and update cycles are supported to ensure that all dependencies are taken into account, and reboots occur if required by specific updates.

Management of Cluster Shared Volumes (CSV) is also integrated into the Failover Cluster Manager. A CSVFS designator is used in storage management tools to indicate the use of CSV enabled volumes. CSV volumes are still formatted as an NTFS file system, but now applications can be aware that they are running on top of a CSV volume. In addition, CSV can make use of SMB 2.2 to perform metadata updates, and integrates with SMB 2.2 multi-channel support to stream traffic across multiple SMB sessions to achieve high-throughput. CSV also takes advantage of SMB 2.2 over RDMA for high-performance applications. In terms of security, Windows Server 8 now supports Bit Locker on CSV as well as non-CSV disks.

The backup of CSV volumes is also greatly simplified in Windows Server 8, allowing for parallel backups to take place for different CSV volumes across multiple cluster nodes. It is also no longer a requirement to change the CSV volume ownership to the cluster node performing the backup in Windows Server 8.

Monitoring is improved in Windows Server 8, allowing monitoring of the complete stack in a continuously-available cloud infrastructure including:

  • Monitoring of heartbeat between cluster nodes
  • Monitoring of the heartbeat between kernel mode driver and user mode service (e.g., to identify user mode hangs)
  • Monitoring of the Hyper-V services health
  • Monitoring of virtual machine health
  • Monitoring of applications running in a virtual machine

Windows Server 8 also allows the identification of application failures and can take action for application recovery.

Continuous-Availability Solutions with Block Storage

In Windows Server 8, continuous-availability solutions can be built using traditional block storage environments including Fibre-Channel or iSCSI SANs, as well as with SAS RBOD (external SATA drives), SAS JBOD, Windows Server 8 Spaces (software-based disc virtualization),and FCoE or SMB 2-based solutions. Windows Server 8 still supports specialized hardware, software, or application replication configurations in addition to the out-of-the-box features for continuous-availability solutions.

Continuous-Availability Solutions with Remote File Storage

Making use of the SMB 2.2 protocol, Windows Server 8 enables the in-box File Server as an alternative storage solution for continuous-availability server applications, including Hyper-V based cloud infrastructures. A clustered File Server supports transparent failover of shares on nodes including the auto-recovery of file connections and handles to server applications. File Server transparent failover allows recovery in the case of planned hardware or software maintenance of cluster nodes and unplanned cluster node failures. On the client side, SMB 2.2 supports transparent failover through sessions which maintain a high-level communication path while allowing the underlying network connection to be torn down and reconnected between physical nodes. A new SMB Witness Protocol allows faster session reconnections after a failover by providing an active indication to the client of a failure rather than depending on a network timeout.

SMB 2.2 supports the use of active-active shares, which allows a single share to span multiple nodes, providing support for high-bandwidth scenarios such as a Hyper-V based cloud. Active-active shares require the use of a failover cluster and CSV. This configuration presents a single logical file server with a single file system namespace (avoiding drive letter limitations) across a file server cluster, eliminating the need to manage cluster disk resources. File Server cluster nodes are registered under a common DNS entry, a Distributed Network Name (DNN), and load balanced based on a DNS round-robin scheme. This implementation requires a complete SMB 2.2 client and server based deployment. In terms of backup and restore, VSS supports consistent shadow copies for data stored on File Server shares.

As with block storage, continuous-availability solutions based on Windows Server 8 File Server can be deployed using traditional Fibre-channel or iSCSI SANs, and alternatives such as Spaces over shared JBOD SAS. A variety of bandwidth intensive scenarios are supported through 1 Gb and 10 Gb Ethernet network interfaces, as well as InfiniBand.

Continuous-Availability Solutions with Network Access Storage

In addition to block storage file server storage, Windows Server 8 can support continuous-availability solutions through compatibility with Network Access Storage (NAS) appliances. Microsoft is working with storage companies, NetApp and EMC, to integrate SMB 2.2 into their NAS stacks to support infrastructures, like Hyper-V, that require a high degree of performance and scalability.


In this article, you learned about Windows Server 8 continuous-availability scenarios with different storage solutions that can support cloud deployments. In Part 8 of this series, you will learn about the networking support in Microsoft Windows Server 8 that accommodates a wide range of cloud deployment scenarios and performance requirements.

If you would like to read the other parts in this article series please go to:

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