Unlike replication, which works at the logical level, database mirroring works at the level of the physical log record. Beginning in SQL Server 2008, the principal server compresses the stream of transaction log records before sending it to the mirror server. This log compression occurs in all mirroring sessions.

SQL Server provides 3 operating modes for database mirroring and the exact mode is based on the setting of transaction safety and whether a witness server is part of the mirroring session.

With database mirroring, you have the option of deploying in one of three modes: high safety with automatic failover mode (high availability with a witness server), high safety without automatic failover mode (high protection without a witness server), and high-performance mode.

Mirroring is the copying of data or database to a different location. While replication is the creation of data and database objects to increase the distribution actions.

SQL Server database mirroring is a disaster recovery and high availability technique that involves two SQL Server instances on the same or different machines. One SQL Server instance acts as a primary instance called the principal, while the other is a mirrored instance called the mirror.

Database mirroring maintains two copies of a single database that must reside on different server instances of SQL Server Database Engine. When a database mirroring session is synchronized, database mirroring provides a hot standby server that supports rapid failover without a loss of data from committed transactions.

A database mirror is a complete backup of the database that can be used if the primary database fails. Transactions and changes to the primary database are transferred directly to the mirror and processed immediately so the mirror is always up-to-date and available as a “hot” standby.

Finally, with database mirroring, the mirror database is always in a state of recovery, which essentially means it can’t be used while mirroring is active. With AlwaysOn, the replica databases provide read-only access to use for reporting and backup purposes, offloading some of the workload from the primary server.

Database Mirroring is used to move the database transactions from one SQL Server database (Principal database) to another SQL Server database (Mirror database) on a different instance. In SQL Server Log Shipping and Mirroring can work together to provide solutions for high availability and disaster recovery.

Server mirroring is a process in network management through which an exact replica of a server is continuously created on run time. Duplicating the entire contents of a server on another remote or in-house server allows data to be restored if the primary server fails.

Database mirroring is a solution for increasing the availability of a SQL Server database. Mirroring is implemented on a per-database basis and works only with databases that use the full recovery model.

Operating modes. SQL Server database mirroring can be set to provide high availability or disaster recovery. Depending on the needs, a DBA can choose among three available modes High safety – Data is written and committed on the principal and mirror databases synchronously. Only after committing on both databases,…

Synchronous mirroring : In all SQL Server databases, data changes are recorded in the transaction log before any changes to actual data pages are made. The transaction log records are placed first in a database’s log buffer in memory, and then flushed to disk (or ‘hardened’) as quickly as possible.

In database mirroring, the partner whose database is currently the principal database. Received transaction log records that are waiting on the disk of a mirror server. The principal server and mirror server perform complementary principal and mirror roles.