Advantages and disadvantages of SQL Server cluster Server

A "virtual" server consisting of two or more physically independent servers is called a clustered server. A Microsoft service called Microsoft Cluster Services (MSCS) can manage a clustered server. A SQL Server cluster is a virtual server that consists of two or more servers (nodes) running SQL Server. If one node in the cluster fails, the other node in the cluster assumes responsibility for the failed node.
It is a common misconception that a SQL Server cluster can load balance two nodes in a cluster. Although this may seem useful, it is not true. This also means that cluster SQL Server does not really improve performance. Cluster SQL Server can only provide failover functionality. Failover is when a machine in the system fails to function, and another machine takes over the instance of SQL Server running it. The failure of this function may be due to hardware failure, service failure, manual failure, or various other reasons.
why cluster SQL Serverenvironment?
In terms of practicality, the clustered SQL Server environment is satisfying. When a failover occurs, the time to transfer a DB instance from one server to another is very short, typically only 3-7 seconds. Although the connection needs to be rebuilt, failover processing is usually transparent to the end user of the database. Low failover costs can also help you maintain the nodes in your cluster without making the server completely inaccessible.
SQL ServerCluster Type
There are two types of SQL Server clusters: Active/passive clusters and active/active clusters. They are explained separately below (the two-node SQL Server cluster is based).
Active/Passive cluster
In this type of cluster, only one node at a time controls SQL Server resources. The other node is always in standby mode, waiting for the failure to occur. When failover occurs, the alternate node obtains control of the SQL Server resource.
Advantages:Because there is only one instance running on the server, no additional server is required to take over two instances of SQL Server when failover occurs, and performance is not reduced. 
Disadvantages: Because there is only one instance of SQL Server running on the virtual server, the other server always handles standby mode with idle state. This means that you are not taking full advantage of the hardware you purchased.
Active/Active cluster
In this type of cluster, each node in the cluster runs a separate and active instance of SQL Server. In the event of a node failure, another node is able to control the instance of SQL Server where the failed node occurs. The normal node will then run two instances of SQL Server-its own instance and the failed instance.
Advantages: With this configuration, you can make the most of your hardware. In such a system, two servers are running, not just one server, and the other is in standby mode waiting for failure, so you can make the most of the machines you buy.
Disadvantages: If a server runs two instances of SQL Server while a failover occurs, performance can be adversely affected. However, performance degradation is always much better than virtual server failure. Another failure of this configuration is that it requires more licenses to be purchased than active/passive clusters. Because the cluster is running two active SQL Server instances, this requires you to purchase two separate server licenses. In some cases, this can also be a hindrance to you.
Cluster Considerations
In terms of high practicality, the clustered SQL Server environment has some advantages. However, high practicality does accompany some kind of compromise.
First, it is very expensive to build a clustered SQL Server environment. This is because the nodes in the cluster must follow the cluster node compatibility list. Also, a complex network needs to be built, the machines must be configured almost identically, and the database file disk subsystem sharing is required. A Storage Area network (SAN) is a good choice for building such subsystems, but sans are not necessary and expensive. Also, if you are running an active/active cluster, you need to purchase a license for the processor of each machine running the instance of SQL Server in the cluster.
Because local clusters are primarily confined to the same geographic region, natural disasters can completely malfunction the cluster. In that case, you need to move to the disaster recovery site to continue. You can also build geographically dispersed SQL Server clusters, but such systems are more complex and expensive.

Advantages and disadvantages of SQL Server cluster Server