In the world of IT operations, business continuity and disaster recovery is always a paramount concern for administrators. Ensuring high availability for applications, particularly for database services, is crucial. In this context, Microsoft Azure’s Always On Failover Cluster Instances (FCI) provides a high availability solution for SQL Server instances by leveraging the technology of Windows Server Failover Clustering (WSFC).
This article presents a discussion on how to configure Always On FCI on Azure Virtual Machines, providing practical guidance for those aspiring to take the DP-300 Administering Microsoft Azure SQL Solutions examination.
Always On Failover Cluster Instances
FCI utilizes Windows Server Failover Clustering (WSFC) functionality to provide local high availability through redundancy at the server-instance level. A failover cluster is a combination of one or more nodes (servers) with two or more shared disks, known as a “failover cluster instance.” The clustered servers are connected by physical cables and by software. If one of the cluster nodes fails, another node begins to provide service (a process known as failover).
Configuring Always On FCI on Azure Virtual Machines
- Setup WSFC: The first step in implementing Always On FCI in Azure VMs is to set up the Windows Server Failover Clustering. It requires a minimum of two VMs in the same Azure region, but in different fault domains. Once the VMs are in place, install the Failover Clustering feature, and create a new cluster using the Failover Cluster Manager.
- Configure Shared Disk: Implementing Always On FCI requires a shared disk that will be used to store the SQL Server data and log files. Azure Shared Disks can be used for this purpose, which should be configured post the WSFC setup.
- Install SQL Server: Once the shared disk is in place, install a clustered SQL Server instance. It’s essential to choose the SQL Server Failover Cluster installation option in the SQL Server Setup program.
- Create Load Balancer: To manage the network traffic to the SQL Server FCI, an Azure Load Balancer should be created which will hold an IP address for the SQL Server FCI. This IP address will be used by applications to connect to the SQL Server FCI.
- Test the Setup: Once everything is configured properly, simulate node failures to test if failover is happening as expected.
Following these steps, you can successfully deploy Azure Always On Failover Cluster Instances in Azure Virtual Machines.
Examples, comparisons, and clarifications
Although not expressly asked for in the original request, providing practical, real-life examples or comparisons can further aid understanding. For example, you might compare an Always On FCI configuration to an alternative Azure high availability solution – such as Always On availability groups, Azure SQL Database, or Azure SQL Managed Instance. Each of these has different strengths, weaknesses, prerequisites, and levels of complexity involved in configuration.
The keys differences between Always On FCI and Always On Availability Groups are that FCI uses shared storage between all nodes in the FCI while Availability Groups use separate storage for each node in the group.
Conclusion
To summarize, correctly configuring Always On FCI in Azure VMs is a critical task for database administrators to ensure high availability for their SQL Server instances, thereby achieving the aim of business continuity. By following these guidelines and standard best practices from official Microsoft documentation, you are well-prepared to take on this domain and apply these concepts in the DP-300 Administering Microsoft Azure SQL Solutions examination.
Practice Test
True/False: To set up Always On Failover Cluster Instances (FCI) on Azure virtual machines, Azure Load Balancer is necessary.
Answer: True
Explanation: Azure Load Balancer is essential for setting up Always On FCI in Azure VMs. It helps distribute the traffic to the active node and handles automatic failover.
Which of the following is NOT necessary for configuring Always On FCI on Azure VMs?
- a) Azure VMs
- b) Azure Load Balancer
- c) SQL Server instances not enabled for AlwaysOn
- d) Azure Shared Disks
Answer: c) SQL Server instances not enabled for AlwaysOn
Explanation: All the options except (c) are necessary. SQL Server instances must be enabled for AlwaysOn for the FCI to work properly.
True/False: You can set up Always On FCI with SQL Server 2014 Standard edition.
Answer: False
Explanation: Always On FCI is only available for SQL Server 2016 and higher versions, including all editions of SQL Server
Which of the following components of Always On FCI on Azure VMs helps in automatic failover?
- a) Azure VMs
- b) SQL Server instances
- c) Azure Load Balancer
- d) Azure Disk Storage
Answer: c) Azure Load Balancer
Explanation: Azure Load Balancer helps in automatic failover by redirection of client traffic to the currently active node.
True/False: We can use MySQL instances to set up Always On FCI on Azure VMs.
Answer: False
Explanation: Always On FCI can only be set up with SQL Server instances, not with instances of other database types including MySQL.
Which of the following cannot be given as quorum witness in Always On FCI on Azure VMs?
- a) Shared Disk
- b) Cloud Witness
- c) File Share Witness
- d) MySQL Server
Answer: d) MySQL Server
Explanation: MySQL Server cannot be used as a quorum witness. Only Shared Disk, Cloud Witness, and File Share Witness can be used.
True/False: You can use Azure Files as a cloud-based file share witness for Always On FCI.
Answer: True
Explanation: Azure Files can indeed be used as a cloud-based file share witness.
Can you host multiple SQL Server FCI instances on the same set of nodes?
- a) Yes
- b) No
Answer: a) Yes
Explanation: As long as each FCI instance uses separate Azure shared disks, you can host multiple SQL Server FCI instances on the same set of nodes.
True/False: AlwaysOn Availability Groups (AGs) and Failover Cluster Instances (FCIs) cannot work together.
Answer: False
Explanation: AlwaysOn AGs can provide database-level failover over any network, complementing the server-level failover provided by FCIs.
Which of the following protocols is not supported by Azure Load Balancer, used for Always On FCI on Azure VMs?
- a) TCP
- b) UDP
- c) HTTP
- d) ICMP
Answer: d) ICMP
Explanation: Azure Load Balancer supports TCP, UDP, and HTTP, but not ICMP.
During FCI set up, in which scenario SQL Server Agent should be manually started?
- a) During Installation
- b) During Configuration
- c) After Configuration
- d) Never
Answer: b) During Configuration
Explanation: During configuration, the SQL Server Agent should be manually started as it is necessary to the process.
True/False: Both public and private IP addresses are required in the setting up of Always On FCI on Azure VMs.
Answer: True
Explanation: Both a public and private IP are needed to set up Always On FCI for the allocation and routing of resources.
What role does a quorum play in a SQL Server FCI on Azure VMs?
- a) It helps with load balancing
- b) It helps with connectivity
- c) It prevents split-brain scenario
- d) It helps with traffic management
Answer: c) It prevents split-brain scenario
Explanation: A quorum plays a critical role in preventing split-brain scenarios i.e., it helps to determine which nodes are active.
True/False: Always On FCI is only supported on Windows Server 2016 and later versions.
Answer: False
Explanation: Always On FCI supports Windows Server 2012 R2, 2016, and
Which storage account type is not compatible for setting up AlwaysOn FCI in Azure VMs?
- a) Premium File Shares
- b) Standard File Shares
- c) Azure Blob Storage
- d) Azure Disk Storage
Answer: c) Azure Blob Storage
Explanation: Azure Blob Storage cannot be used for setting up AlwaysOn FCI as it doesn’t support clustered roles.
Interview Questions
What is the main purpose of Always On Failover Cluster Instances in Azure virtual machines?
Always On Failover Cluster Instances provide high-availability for an on-premises infrastructure in a cloud service model. They ensure that even if one instance fails, there’s another instance ready to take on the load with minimal disruption to the service.
Which technology does Always On Failover Cluster Instances in Azure utilizes to achieve high availability?
Always On Failover Cluster Instances utilizes Windows Server Failover Clustering (WSFC)technology.
What is a prerequisite for configuring an Always On Failover Cluster Instances on Azure virtual machines?
An active Azure account and a running Azure Active Directory domain service are prerequisites for setting up Always On Failover Cluster Instances on Azure virtual machines.
What is the main difference between an Azure availability set and availability zone?
Azure availability set is a logical grouping of VMs within a data center that allows Azure to understand how to update VMs and how they are isolated from each other. Availability zones, on the other hand, are unique physical locations within a region. Each zone is made up of one or more data centers equipped with independent power, cooling, and networking.
How many nodes do you need to configure Always On Failover Cluster Instances on Azure VMs?
You need at least two nodes to configure Always On Failover Cluster Instances on Azure VMs.
How do I add a disk to the SQL Server VM instances when configuring Always On Failover Cluster Instances on Azure virtual machines?
You can add a disk to the SQL Server VM instances from the Azure portal by selecting your SQL Server VM and clicking “disks”, then clicking “+Add data disk”.
Can you have cross-region Always On Failover Cluster Instances on multiple Azure VMs?
No, Always On Failover Cluster Instances on Azure VMs must reside within the same region.
What is a quorum for a Windows Server Failover Clustering (WSFC)?
A quorum is a collection of practices that WSFC uses to calculate the number of failures that the cluster can sustain while still remaining online.
What is Azure Load Balancer role in Always On Failover Cluster Instances?
Azure Load Balancer distributes incoming internet traffic to backend SQL Server VMs based on the configurations and rules that you set. It enables you to achieve better availability and reduces latency.
Can you use Azure Managed Disks with Always On Failover Cluster Instances?
Yes, Azure Managed Disks are recommended to use with Always On Failover Cluster Instances as they provide better management, reliability, and scalability features.
Which operating systems are currently supported for Always On Failover Cluster Instances on Azure VMs?
The supported operating systems for Always On Failover Cluster Instances on Azure VMs are Windows Server 2012 R2 and later.
What storage options are supported for SQL Server data files in Azure when configuring Always On Failover Cluster Instances?
SQL Server data files in Azure can be stored on Azure Managed Disks, Storage Spaces Direct (S2D), or Azure Shared Disks.
In the context of Azure virtual machines, what does “Failover” stand for?
In Azure VMs, “Failover” is a process when if the primary node goes down, the service is automatically switched to a secondary node ensuring high availability and disaster recovery.
How could you perform a manual failover of an Always On failover cluster instance?
To manually failover an Always On failover cluster instance, you would move the active role of primary replica to a synchronized secondary replica.
Why would the automatic failover of an Always On failover cluster instance not occur?
Automatic failover of an Always On failover cluster instance might not happen if the secondary replica is not synchronized or if the failover mode for the secondary replica is set to manual.
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