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Malte · 08-16-2017, 02:47 PM

Hello,

can anyone help? What is the difference between the Microsoft solution always on and failover cluster? And what is the better solution for high awailability?

geforceGTX · 08-17-2017, 09:34 AM

Hello,
Always on is the Microsoft commercial name for some High Availability features, which include the failover cluster instances and availability groups for SQL servers.
The biggest difference is that a clustered instance example ‘one’ and ‘two’ has the same binaries installed and configured on cluster nodes (can be physical or virtual servers) the database files should be sitting on a shared disk. But only one of the two nodes at a time can own the data disks and run the SQL Server instance (in active node) and all other nodes are in slave mode (passive). When the node fails for any reason, the disks are moved to one of the passive nodes and the service is started again, and making it to active node. All clients connecting to the clustered network name network name, which is moved to the active node, please make sure that all clients are able to connect to the active node.

With high availability Groups, with two or more copies of the same database are synchronized across over multiple nodes (servers). In this case you don't have a single copy of the database files, but you have multiple copies (replicas). One of those copies is read and/or write, while all other copies are read-only. To ensure that the clients are connecting to the appropriate replica, a virtual network name is used, which is similar to what the cluster virtual network name does. With an additional connection string property, you can control whether you're hitting the read/write or read-only replica.