High Availability (HA) of the server of Database is the solution( process, technology ) to make the application database available 24x7 under either planned or un - planned conditions.
There are five type of options in MS SQL Server to achieve and configure a setup for high availability solution for the databases.
Replication
The source(Main) data will be copied to destination, through replication agents (jobs). Object level technology.
Main terminology
- Publisher is source server.
- Distributor is optional and stores replicated data in a suitble environemt for the subscriber.
- Subscriber is the destination server.
Log Shipping
The source data will be copied to destination through Transaction Log backup jobs. Various Database level technology.
Main terminology
- Primary server is source server.
- Secondary server is destination server.
- Monitor server is optional and will be monitored by log shipping status.
Mirroring
The primary data will be copied to a secondary through a network transaction basis with help of mirroring endpoint and port number. Database level technology.
Main terminology
- Principal server is source server always.
- Mirror server is destination server always.
- Witness server is optional and can be used to make automatic failover.
Clustering
The data will be stored in shared location which is used by both primary and secondary servers based on availability of the server. Instance level technology. Windows Clustering setup is required with shared storage
Main terminology
- Active node is where SQL Services are running.
- Passive node is where SQL Services are not running.
AlwaysON Availability Groups
The primary data will be copied to secondary through network transaction basisand Group of database level technology. Windows Clustering setup is required without shared storage for ALwaysON Availibilty Groups.
Main terminology
- Primary replica is source server.
- Secondary replica is destination server.
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