January 26, 2011 at 9:09 am
Hello Experts
I need some suggestions regarding the implementation of Database Mirroring to one of the Production database servers.
It has to be decided whether to go by Synchronous or Asynchronous Database Mirroring.
Can you please suggest on what ground we choose 'Synchronous' and 'Asynchronous' Database mirroring? It has been told to me that, the network speed is pretty good between the servers where the database mirror has to be set. But if incase, the connection breaks or due to slow network, the wait time to the commands will be increased in Synchrounous model, so problem might occur since it has to wait for an acknw from Mirrored Database.
Please suggest the distinctive features so that I can choose the right one.
Thanks.
January 26, 2011 at 10:05 am
That of course depends on size of your database/transaction and how much data are you willing to lose in case you lose primary server.
With synchronous mirroring, the primary server does not commit an operation to the database until it has also been written to the mirror server, meaning no data should be lost if the primary server fails. The mirror then returns a write confirmation back to the primary server. The disadvantage of synchronous mirroring is that the primary server’s performance can be limited by the time it takes for a database operation to be written to the mirror server. When the latency between the two servers is low, however, the performance impact is usually also low. Synchronous mirroring also allows using a witness server to provide automatic failover, an option not available with asynchronous mirroring. This witness server monitors the primary server and initiates a failover if the witness and the mirror server lose their connection to the primary server but the witness remains connected to the
mirror server. When database clients reconnect, they are automatically rerouted to the mirror server, which has become the new primary server.
With asynchronous mirroring, the primary server does not wait for the mirror server to commit operations to disk. The disadvantage of asynchronous mirroring is that data can be lost because of the delay between the primary server writing data to disk and the mirror server writing that data to disk. However, this delay is usually small, so the amount of data potentially lost in such a scenario is typically minimal.
January 26, 2011 at 10:17 am
Thanks Alex... Looking like at this way, Synchronous would be good.
By the way, let me know if there is any good document available to implement Sync DB- Mirroring (with step by step screen shots).
Thanks.
January 27, 2011 at 12:42 pm
January 28, 2011 at 7:20 am
I recently set up synchronous mirroring and wrote a couple blog posts about my experiences. Overall, it was very easy. My first post about it is here[/url]. There is also a link in that post to a video someone made showing you exactly how mirroring is setup and how it works. Very useful. Search my blog for the tag "mirroring" to get more articles related it - such as configuring alerts. Also note that, in order for your clients to know if a failover occurred, you'll need to update your ODBC drivers to one that is mirroring aware.
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