Standalone SQL Server instances usually store their databases on local disk storage or nonshared disk storage; clustered SQL Server instances store data on a shared disk array. To ensure the integrity of the databases, both nodes of a cluster never access the shared disk at the same time. This shared disk array must have at least two logical disk partitions.
When both cluster nodes are up and running and participating in their respective active and passive roles, they communicate with each other over the network. For example, if you change a configuration setting on the active node, this configuration is propagated automatically, and quickly, to the passive node, thereby ensuring synchronization.
As you might imagine, though, you can make a change on the active node and have it fail before the change is sent over the network and made on the passive node. In this scenario, the change is never applied to the passive node. Depending on the nature of the change, this could cause problems, even causing both nodes of the cluster to fail.
To prevent this change from happening, a Windows Failover Cluster employs a quorum. A quorum is essentially a log file, similar in concept to database logs. Its purpose is to record any change made on the active node.
This way, should any recorded change not get to the passive node because the active node has failed and cannot send the change to the passive node over the network, the passive node, when it becomes the active node, can read the quorum log file to find out what the change was.
The passive node can then make the change before it becomes the new active node. If the state of this drive is compromised, your cluster may become inoperable. Additional benefits for clustering include simplicity for installation of SQL and ease of administration and maintenance.
There is plenty to consider when planning on clustering SQL Server. Hopefully you were able to get a better understanding of what clustering is and an idea of the terminology associated with clustering SQL Server In the remaining tips in this series we will review these items in greater detail, walking you through the decisions you'll make on architecture, the installation process, the tools available to monitor the state of the cluster and its resources, as well as comparing clustering to the other high-availability options associated with Microsoft SQL Server.
Getting started with SQL Server clustering. Related Articles. What's the Quarantine state in Windows Failover Clusters. Popular Articles. Rolling up multiple rows into a single row and column for SQL Server data. How to tell what SQL Server versions you are running. Resolving could not open a connection to SQL Server errors. Ways to compare and find differences for SQL Server tables and data. Searching and finding a string value in all columns in a SQL Server table.
View all my tips. Back To Top Dear Sir, How to map a single user in multiple databases in a single instance. My Scenario is example my user name is xxxx. So how i map this user without using wizards. Please Provide any scripts that will save me lot my time. Thanks, Rajesh. To successfully set up of a failover cluster instance, use the documentation and procedures for SQL Server. Before you install Configuration Manager, prepare the failover cluster instance to support Configuration Manager.
This service supports the Backup Site Server maintenance task. After the site installs, Configuration Manager checks for changes to the cluster node each hour. Configuration Manager automatically manages any changes it finds that affect its component installs. For example, a node failover or the addition of a new node to the failover cluster instance.
Configuration Manager supports the following options for failover cluster instances used for the site database:. The site database server must be remote from the site server. The cluster can't include the site server. The Configuration Manager setup process doesn't block installation of the site server role on a computer with the Windows role for Failover Clustering. SQL Server Always On availability groups require this role, so previously you couldn't colocate the site database on the site server.
With this change, you can create a highly available site with fewer servers by using an availability group and a site server in passive mode. For more information, see High availability options. Add the computer account of the site server to the local Administrators group of each server in the cluster.
The Named pipes protocol isn't required, but can be used to troubleshoot Kerberos authentication issues. There are specific certificate requirements when you use a failover cluster instance for the site database. For more information, see the following articles:.
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