SQL Server Clustering: The What and Why
SQL Server clustering is the term used to describe a collection of two or more physical servers (nodes), connected via a LAN, each of which host a SQL server instance and have the same access to shared storage. Clustering SQL servers provides high availability and protection from disasters whenever a server hosting the SQL Server instance fails.
If you are on a standalone server, a hardware failure can bring your operations to a halt. However, with clustering, if a node has problems, you can automatically failover to another node – with minimal downtime – and continue to let your users keep working while IT works to resolve the problem. When the primary server is fixed, you can quickly revert operations back.
When compared to using a stand-alone server, SQL Server clustering can also limit downtime when applying upgrades and security patches.
While SQL Server clustering provides high availability and minimizes system downtime, SQL Server clustering will not improve the performance of the servers or applications. To improve performance, you need to upgrade the computing power of the servers.
This article introduces SIOS SQL Server Clustering Solutions and provides a high-level comparison of SIOS versus Microsoft’s SQL clustering solutions.
SIOS SQL Server Clustering Solutions
SIOS Technology Corp. offers high availability clustering solutions that help you automatically recover from infrastructure and application failures. To support SQL Server high availability, SIOS offers two solutions:
- SIOS DataKeeper Cluster Edition runs on Windows and leverages Microsoft Windows Server Failover Clustering (WSFC) to provide SQL Server clustering with shared storage (SAN) or without shared storage (SANless). A SANless environment eliminates single point of failure, improves replication efficiency, protects applications other than SQL Server, and protects distributed transactions and system databases.
- SIOS Protection Suite for Linux is a tightly integrated combination of failover clustering, continuous application monitoring, data replication, and configurable recovery policies to protect business-critical applications and databases, including SQL Server, in a SAN or SANless environment.
Let us take a closer look at the features and benefits of each solution.
SIOS DataKeeper Cluster Edition
Windows Server Failover Clustering (WSFC) is a feature of the Windows Server platform that improves high availability. WSFC is commonly used to provide high availability for applications using SQL Server. In the event of a server or application failure, WSFC coordinates redundant computing resources and automatically manages the recovery of SQL Server operations and data on a standby node. Unfortunately, if you want to run your SQL Server application in the cloud, there is no SAN available.
SIOS DataKeeper Cluster Edition allows you to easily create a SANless WSFC to achieve high availability and disaster recovery for your SQL Server applications operating in the cloud, in virtualized environments such as VMware or Hyper-V, or on physical servers using only local storage. While WSFC manages the software cluster, SIOS cluster software synchronizes local storage using real-time (synchronous or asynchronous) block-level replication. The synchronized storage appears to WSFC as a traditional SAN-based storage. You can also build hybrid cloud configurations for disaster recovery protection between an on-premises data center and the cloud.
SIOS DataKeeper Cluster Edition software is fully certified by Microsoft and operates with Enterprise-Class availability in any configuration across cloud regions and zones.
SIOS SANless clusters not only eliminate the cost, complexity, and single-point-of-failure risk of a SAN, you can also use the latest in fast PCIe Flash and SSD storage for performance and protection in a single cost-efficient solution.
SIOS Protection Suite for Linux
SIOS Protection Suite for Linux includes:
- SIOS LifeKeeper, which provides flexible failover clustering software that monitors the entire application stack; it orchestrates failover of the SQL Server application in compliance with best practices
- SIOS DataKeeper, which provides fast, efficient host-based, block-level data replication for mirroring local storage in a SANless cluster configuration or replicating to remote locations or cloud for disaster recovery
- Multiple Application Recovery Kits (ARKs) which provide application intelligence with automated configuration and validation to protect your business-critical applications and data from downtime and disasters.
While SIOS Protection Suite can operate in a SAN environment to support a traditional HA hardware-based cluster, it can also be used to create a shared-nothing approach to server clustering allowing it to run SANless. It delivers a robust, versatile, and easily configurable solution with automatic and manual failover/failback recovery policies for a wide variety of applications.
SIOS Versus Microsoft SQL Clustering Solutions
There are other SQL Server clustering solutions available on the market. Some of the most popular SQL Server clustering solutions are offered by Microsoft and include:
- SQL Server Basic Availability Groups
- SQL Server Always On Availability Groups
- SQL Server Failover Cluster Instances with Shared Storage
SQL Server Basic Availability Groups runs on Windows and supports a maximum of a two-node cluster. It works like a database mirroring solution. While clustering and mirroring are both methods to improve high availability, mirroring only allows the database to failover. If you have other services, files, and other resources outside of SQL that you need after a failover, or if you have several databases that must stay together, clustering is the better solution.
SQL Server Always On Availability Groups runs on both Windows and Linux and according to Microsoft, it “provides an enterprise-level alternative to database mirroring.” It requires costly SQL Server Enterprise Edition.
You can save as much as 70 percent on software licensing costs and get enterprise-class clustering features by using SQL Server Standard Edition with SIOS’ SQL clustering solutions.
SQL Server Failover Cluster Instances with Shared Storage runs on both Windows and Linux. It is a single-site solution and requires a SAN.
Unfortunately, SANs are expensive to purchase and maintain, require SAN administrative expertise, and are a single point of failure. A SAN can also negatively impact database performance.
You can find a more detailed comparison of the strengths and weaknesses of SQL Server Always On, SQL Server Failover Cluster, and SIOS DataKeeper Cluster Edition here.
SQL Server Clustering in the Cloud
SIOS DataKeeper and SIOS Protection Suite for Linux provide high availability and disaster recovery protection for Windows and Linux applications respectively, operating in any combination of physical, virtual, cloud, or hybrid cloud infrastructures. For example, SIOS DataKeeper can:
- Protect critical on-premise or hybrid business applications, including SQL Server, to high availability Windows or Linux environments in AWS, Azure, or Google Cloud.
- Protect your SQL Server cloud application by creating a Windows or Linux cluster in AWS, Azure, or Google Cloud.
- Provide sitewide, local, or regional high availability and disaster recovery protection by failing over SQL Server instances across cloud availability zones or regions.
SIOS DataKeeper Cluster Edition and SIOS Protection Suite for Linux both simulate clustered shared storage and can provide fully certified high availability cluster protection across cloud regions and availability zones.
SIOS provides offerings that support a breadth of applications, operating systems, and infrastructure environments, providing a single solution that can handle all your high availability needs. Here are just a few examples that demonstrate the power of SIOS.
- PayGo (paygoutilities.com) implemented SIOS DataKeeper with WSFC to provide high availability for SQL Server on AWS.
- A healthcare information service provider uses SIOS DataKeeper to protect their important SQL Server in more than 18 cluster nodes, eliminating bandwidth issues, improving data protection, and reducing downtime in their critical healthcare network environment.
- Mavis Discount Tire uses SIOS DataKeeper Cluster Edition to deliver high availability for their business-critical SQL Server.
If you are looking for a high availability/disaster recovery solution to protect SQL Server in either a Windows or Linux environment, you can find more information here.