![]() Their marketing material says that the change is at a very low I/O level thereby “almost” guaranteeing no file corruption but if you read the fine print, they can’t guarantee no corruption. Overview: This is a block level file replication option that works by monitoring the database and log files and replicating any changes in them to the other server. ![]() Also, the witness server doesn’t have to be an expensive server since it is just designed to provide a quorum. In our situation we prefer the 1st mode because we desire immediate failover and our software is written using ADO which is designed to handle failing over if the 1st connection fails. We have seen issues with database corruption with the 2nd option, but the 1st and 3rd options prevent this. ![]() This is not much of a problem if you have 2 reliable servers equally paired and you can always fail over the individual databases as needed if you prefer them to be in sync on the same server.Ĭonfiguration Point: Depending on your needs, it is in my opinion, to configure SQL Server Database Mirroring in either the 1st or 3rd mode depending if you want automatic failover or not. It is so simple that even a novice IT person should be able to figure it out.Ĭons: The mirroring is on a database by database basis so it is possible that you have the primary and secondary for a group of databases spread across the 2 SQL Servers. A nice thing about this mirroring solution, and something we appreciate, is the simple user interface. The 1st mode requires a witness server to establish a quorum in order for the SQL Servers to know who is the primary and who is the secondary. The 1st mode is the synchronous mode with automatic failover (High availability and Reliability), the 2nd mode is asynchronous without automatic failover (High Performance) and the 3rd mode is synchronous without automatic failover (High Reliability). It has 3 modes for those that desire performance and those that must have reliability. Pros: The advantage of this option is that it is a standard feature of SQL Server and its free. Depending on the mode you choose, the transactions are committed either synchronously or asynchronously. Overview: This works by having SQL Server write each transaction to both SQL Server databases at the same time on 2 different servers so that they are synchronized. SQL Server 2005/2008 Database Mirroring: (Recommended) There are many options out there and there is no right answer, but I thought I would address 2 we have used (SQL Server Database Mirroring and Double-Take) and provide some input as to what we’ve found. We regularly get questions about what is the best way to replicate or mirror SQL Server databases to protect against disaster and to provide high availability.
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