Mirroring / Failover

Question

We have a server/database here in the Local Site.

They we will set up a Database Mirroring with Failover at the DR Site.

The idea is to have the Witness Server in the remote DR Site.

So, when the local site goes down, Auto Failover will make the DR Database

But what happens if the Local Database in the local networking loses its access to the Witness server.

Will it be that

Principal - Disconnected   (because it cannot talk to the Witness Server anymore)

and

Mirror Database is Synchronized but somebody has the bring it to be alive, right?

Answer 1

Please share SQL Server version.

DB Mirroring is not a standard adapted approach for DR cases.

There are so many new approaches have come and mirroring will soon be outdated.

Like AlwaysOn on DB or Instance layer setup which can do the same job for you as per your requirement.

You can check below link to know more on it.

https://msdn.microsoft.com/en-us/library/hh510230.aspx?f=255&MSPPError=-2147217396

To answer your queries:

Yes, somebody has to bring that online and also needs to check if at web layer you have defined the partner part so that web can put their request on web server and depends of what type of DB Mirroring you step up.

Connectivity between Primary, Mirror and Witness play major role as it is being used to decide what to do in case of any of these failed. So better connectivity is required all the time. This is required for all the functionality for such cases.

Link for DB Mirroring is shared below:

https://msdn.microsoft.com/en-us/library/ms189852.aspx

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Santosh Singh

Answer 2

Singh

Thank you for your kind answer, but there are so many reasons why companies do what they do.

So many factors... I know everything you have mentioned in your reply, but it did not answer the question.

Thanks

Answer 3

Thanks! and do understand and respect organization level approaches.

Just curious, please share SQL Server versions to attempt to answer you specifically.

Also, if I could understood you, below part of the message was query:

"But what happens if the Local Database in the local networking loses its access to the Witness server.

Will it be that Principal - Disconnected   (because it cannot talk to the Witness Server anymore)

and Mirror Database is Synchronized but somebody has the bring it to be alive, right?

"

Principal - Disconnected   (because it cannot talk to the Witness Server anymore)

Need some clarity, is Mirror and Witness are connected and Principal has lost connection to both or Principal  is still connected to Mirror?

Some good links:

What happens if witness goes down, from another aspect: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/af887f2a-cdb1-4330-93f0-a8444d3bd981/what-happen-if-the-witness-down?forum=sqldatabasemirroring

If Principal is down: http://sql-articles.com/articles/high-availability/how-can-i-bring-mirror-database-online-after-principal-server-is-down/

http://sqlblog.com/blogs/tibor_karaszi/archive/2010/04/16/mirroring-what-happens-if-principal-loses-contact-with-both-mirror-and-wittness.aspx

How Witness effects overall DB mirroring: https://msdn.microsoft.com/en-us/library/ms189902.aspx

 

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Santosh Singh