Hello, cluster fans. This is Mario Liu and I am a Support Escalation Engineer on the Windows High Availability team in Microsoft CSS Americas. I have a good news for you that starting in April 2015, Microsoft will support Windows Server Failover Cluster (WSFC) on Azure IAAS Virtual Machines. Here is the supportability announcement for Windows Server on Azure VMs:
- Windows Failover Cluster Witness
- Windows Failover Cluster Azure
- Windows Failover Cluster Witness
- Windows Failover Cluster Requirements
Install/reinstall the Windows Failover Clustering feature and add the node to a cluster via Server Manager and Failover Cluster Manager. Complete the following steps with a user account that has administrative rights over the cluster, from any server that has access to the cluster.
Microsoft server software support for Microsoft Azure virtual machines
https://support.microsoft.com/en-us/kb/2721672
The Failover Cluster feature is part of that announcement. The above knowledge base is subject to change once more improvements for WSFC on Azure IAAS VMs are made. Please check the above link for the latest updates.
Today, I'd like to share the main differences when you deploy WSFC on-premises as compared to within Azure. First, the Azure VM operating system must be Windows Server 2008 R2, Windows Server 2012, or Windows Server 2012 R2. Please note that both Windows Server 2008 R2 and 2012 both require this hotfix to be installed.
At a higher level, the Failover Cluster feature does not change inside the VM and is still a standard Server OS feature. The challenges are outside and relate to Storage and Network. In this blog, I will be discussing Storage.
The biggest challenge to implementing Failover Clustering in Azure is that Azure does not provide native shared block storage to VMs, which is different than on-premises – Fiber Channel SAN, SAS, or iSCSI. That limits SQL Server AlwaysOn Availability Groups (AG) as the primary use case scenario in Azure as SQL AG does not utilize shared storage. Instead, it leverages its own replication at the application layer to replicate the SQL data across the Azure IaaS VMs.
Until now, we have a few more options to work around the shared storage limitation; and that is how we can expand the scenarios beyond SQL AlwaysOn.
Option 1: Application-level replication for non-shared storage
Some applications leverage replication through their own means at the application layer. SQL Server AlwaysOn Availability Groups uses this method.
Option 2: Volume-level replication for non-shared storage
In other words, 3rdparty storage replication.
A common 3rdparty solution is SIOS DataKeeper Cluster Edition. There are other solutions on the market, but this is just one example. For more details, please check SIOS's website:
DataKeeper Cluster Edition: Real-Time Replication of Windows Server Environments
http://us.sios.com/products/datakeeper-cluster/
Option 3: Leverage ExpressRoute for remote iSCSI Target shared block storage for file based storage from an Azure IaaS VMs
ExpressRoute is an Azure exclusive feature. It enables you to create dedicated private connections between Azure datacenters and infrastructure that's on your premises. It has high throughput network connectivity to guarantee that the disk performance won't be degraded.
One of the existing examples is NetApp Private Storage (NPS). NPS exposes an iSCSI Target via ExpressRoute with Equinix to Azure IaaS VMs.
Availability on Demand – ASR with NetApp Private Storage
https://channel9.msdn.com/Blogs/Windows-Azure/Availability-on-Demand-ASR-with-NetApp-Private-Storage
For more details about ExpressRoute, please see
ExpressRoute
http://azure.microsoft.com/en-us/services/expressroute/
There will be more options to present 'shared storage' to Failover Clusters as new scenarios present in the future. We'll update this blog along with the KB once new announcements become available. As long as you fix the storage, you've built the foundation of the Cluster.
In my next blog, Part 2, I'll go through the network part and the creation of a Cluster.
Stay tuned and enjoy the Clustering in Azure!
Mario Liu
Support Escalation Engineer
CSS Americas | WINDOWS | HIGH AVAILABILITY
One of the powerful features of Windows Server is the ability to create Windows Failover Clusters. With Windows Failover clustering, pools of hardware resources can be bound together in a virtual entity that allows seamlessly hosting resources in a way that is highly available and resilient to failure. Windows Server has certainly evolved over the past several iterations and releases. Now, with Windows Server 2019, Windows Failover Clustering is more powerful than ever and can host many highly available resources for business-critical workloads.
Let's take a look at Windows Server Failover Clustering types and uses for hosting resources.
Windows Server 2019 Failover Clustering Types and Uses
https://tajuncsuri1988.mystrikingly.com/blog/add-a-blog-post-title-d53f769a-315e-480f-8027-2dff554e7db6. As mentioned earlier, the functionality in the latest version of Windows Server is more capable than ever before with various forms of Windows Failover Clustering functionality able to back multiple types of business-critical services.
Let's take a look at the following types of Windows Server 2019 Failover Clustering.
Windows Failover Cluster Witness
- Hyper-V Clustering
- Clustering for File Services
- Scale-Out File Server
- Application Layer Clustering
- Host Layer Clustering
- Tiered Clustering
Each provides tremendous capabilities to ensure production workloads are resilient and highly available.
Hyper-V Clustering
In the realm of virtualization in the enterprise running production workloads, to effectively run Hyper-V in a resilient and highly available fashion, Hyper-V cluster configurations are required. Hyper-V clusters are built on top of Windows Failover Clusters.
How is the Hyper-V cluster architected?
In a traditional Hyper-V cluster, all Hyper-V hosts are connected to shared storage. This allows VMs to reside on storage that all hosts have access to, allowing all hosts to share ownership of the various virtual machines. If a host fails, healthy hosts are able to assume the responsibility of providing compute for the virtual machines assumed from a downed host.
A Hyper-V cluster internally monitors the other Hyper-V hosts so when a host goes down, VMs can be spun up relatively quickly on the healthy hosts. This is done by simply restarting the VMs connected to healthy hosts in the cluster. This highlights the 'Failover' in Windows Failover Clustering.
Clustering is not only beneficial when an unforeseen problem arises; it is also beneficial to perform needed maintenance on a Hyper-V host. Using Hyper-V Live Migration, virtual machines can be moved while they are running to different hosts in the Hyper-V cluster to safely evacuate all workloads from a particular host so that maintenance can be performed.
Hyper-V clustering allows for intelligent load balancing for virtual machines running on top of the Hyper-V hosts that make up the Hyper-V Windows Failover Cluster. Much like VMware vSphere's DRS mechanism, Hyper-V can evaluate Hyper-V hosts and their present load and automatically decide if workloads need to be moved for more efficient placement inside the Hyper-V cluster.
Clustering for File Services
Windows Failover Cluster Azure
The Clustering for File Services Clustering technology has been around perhaps the longest of any of the other types of clustering use cases. This was one of the original ideas behind clustering technology. This was so that file resources could be made highly available in case a single server failed.
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The Clustering for File Services clustering technology works in an active-passive configuration.
Only one file server is active for user connections to files. However, if this active server goes down, the passive server(s) in the cluster will become the active file server that accepts end user connections.
Scale-Out File Server
Traditional Clustering for File Services technology is not robust enough to handle the ever-demanding needs of today's enterprise, especially considering the storage needs to back virtual machines in a Hyper-V Cluster environment.
As mentioned in the previous section, the Clustering for File Services technology is an active-passive configuration. This is not robust enough for high bandwidth, resiliency, and redundancy requirements of virtual hard disk files. This is where Scale-Out File Server or SOFS comes in.
Scale-Out File Server is designed for hosting high-performance workloads such as Hyper-V storage. SOFS allows supporting the requirements of Hyper-V storage. It does this in an active-active configuration of multiple file servers that have persistent connections between them. If one of the SOFS hosts goes down, another SOFS host picks up the workload without any type of migration or failover process. This allows running Hyper-V virtual machines to stay online even during a failure of an SOFS backing file server host.
Application Layer Clustering
Application Layer Clustering is a feature that can be utilized if a service or application needs to have the most uptime possible, regardless of any hardware failures. As already covered, Hyper-V hosts clustered in a Windows Failover Cluster can restart a VM in the event one of the Hyper-V hosts fails. However, this means any applications the VM is hosting will be unavailable during the time required to restart the VM.
If this time of service interruption, albeit brief, is unacceptable, Application Layer Clustering is certainly an option. Application Layer Clustering can be thought of as 'nested' clustering. It involves creating a Windows Failover Cluster using VMs running on top of the physical Windows Failover Cluster hosts. This allows the application to be highly available in addition to the physical Hyper-V hosts backing the Hyper-V Cluster VMs.
Host Layer Clustering
Linux serial terminal program. Dec 31, 2015 A rundown of serial terminal programs that run on Linux. Home Linux Serial Terminal Program Rundown for Linux. December 31, 2015. I figured I'd give a rundown of serial terminals I regularly use on Linux to access consoles on embedded boards through a serial port. I tend to favor both Putty (runs on Windows and Linux) and screen, but a. This is a step-by-step guide to using the serial port from a program running under Linux; it was written for the Raspberry Pi serial port with the Raspbian Wheezy distribution. However, the same code should work on other systems.
Host Layer Clustering is the general term used to describe the technology we have already referred to when talking about Hyper-V Clustering. This is the clustering of the physical Windows Server Failover hosts. This allows clustering two or more physical servers using the Windows Failover Clustering technology to make various roles highly available. Notable among these in today's production data centers is the Hyper-V role.
Windows Failover Cluster Witness
Windows Server 2019 Hyper-V Cluster
Tiered Clustering
When it comes to production workloads, generally the component that matters the most to end users or business stakeholders is the application. However, to ensure that application is resilient and redundant, a tiered clustering approach can be used where both a combination of Host Layer Clustering and Application Layer Clustering are used to ensure both the VM is resilient and redundant (host layer clustering) and the application itself is resilient and redundant (application layer clustering). This allows providing the most resilient configuration possible to ensure the most uptime and high availability for business-critical workloads.
Concluding Thoughts
Clustering technology has certainly evolved from the early days with legacy versions of Windows Server. Windows Server 2019 Failover Clustering types and uses have certainly expanded the various applications of Windows Server Failover Clustering technology and broadened its scope in the enterprise.
Traditional Clustering for File Services technology is not robust enough to handle the ever-demanding needs of today's enterprise, especially considering the storage needs to back virtual machines in a Hyper-V Cluster environment.
As mentioned in the previous section, the Clustering for File Services technology is an active-passive configuration. This is not robust enough for high bandwidth, resiliency, and redundancy requirements of virtual hard disk files. This is where Scale-Out File Server or SOFS comes in.
Scale-Out File Server is designed for hosting high-performance workloads such as Hyper-V storage. SOFS allows supporting the requirements of Hyper-V storage. It does this in an active-active configuration of multiple file servers that have persistent connections between them. If one of the SOFS hosts goes down, another SOFS host picks up the workload without any type of migration or failover process. This allows running Hyper-V virtual machines to stay online even during a failure of an SOFS backing file server host.
Application Layer Clustering
Application Layer Clustering is a feature that can be utilized if a service or application needs to have the most uptime possible, regardless of any hardware failures. As already covered, Hyper-V hosts clustered in a Windows Failover Cluster can restart a VM in the event one of the Hyper-V hosts fails. However, this means any applications the VM is hosting will be unavailable during the time required to restart the VM.
If this time of service interruption, albeit brief, is unacceptable, Application Layer Clustering is certainly an option. Application Layer Clustering can be thought of as 'nested' clustering. It involves creating a Windows Failover Cluster using VMs running on top of the physical Windows Failover Cluster hosts. This allows the application to be highly available in addition to the physical Hyper-V hosts backing the Hyper-V Cluster VMs.
Host Layer Clustering
Linux serial terminal program. Dec 31, 2015 A rundown of serial terminal programs that run on Linux. Home Linux Serial Terminal Program Rundown for Linux. December 31, 2015. I figured I'd give a rundown of serial terminals I regularly use on Linux to access consoles on embedded boards through a serial port. I tend to favor both Putty (runs on Windows and Linux) and screen, but a. This is a step-by-step guide to using the serial port from a program running under Linux; it was written for the Raspberry Pi serial port with the Raspbian Wheezy distribution. However, the same code should work on other systems.
Host Layer Clustering is the general term used to describe the technology we have already referred to when talking about Hyper-V Clustering. This is the clustering of the physical Windows Server Failover hosts. This allows clustering two or more physical servers using the Windows Failover Clustering technology to make various roles highly available. Notable among these in today's production data centers is the Hyper-V role.
Windows Failover Cluster Witness
Windows Server 2019 Hyper-V Cluster
Tiered Clustering
When it comes to production workloads, generally the component that matters the most to end users or business stakeholders is the application. However, to ensure that application is resilient and redundant, a tiered clustering approach can be used where both a combination of Host Layer Clustering and Application Layer Clustering are used to ensure both the VM is resilient and redundant (host layer clustering) and the application itself is resilient and redundant (application layer clustering). This allows providing the most resilient configuration possible to ensure the most uptime and high availability for business-critical workloads.
Concluding Thoughts
Clustering technology has certainly evolved from the early days with legacy versions of Windows Server. Windows Server 2019 Failover Clustering types and uses have certainly expanded the various applications of Windows Server Failover Clustering technology and broadened its scope in the enterprise.
Windows Failover Cluster Requirements
Today's business-critical workloads are required to be more and more resilient and redundant to support 'always on' infrastructure driving today's very web-centric businesses. Windows Server 2019 Failover Clustering supports these new and demanding use cases with a combination of various cluster types and applications of clustering technologies.
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