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Tibor Karaszi

Mirroring: what happens if principal loses contact with both mirror and wittness?

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Published Friday, April 16, 2010 8:46 AM by TiborKaraszi

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Robert L Davis said:

And this is exactly why it is not recommended to have a witness server when running in asynchronous mode. If witness and mirror both go down, then the principal will take itself offline. Without a witness, if the principal becomes disconnected from the mirror, the principal will remain up because it knows that the mirror will not come online automatically.

April 16, 2010 11:30 AM

James Luetkehoelter said:

This also good food for thought about where the witness is placed, near the primary, the the mirror or in between? Or is mirroring even a good choice over a WAN link? Good post!

April 17, 2010 6:39 PM

Ted Krueger (onpnt) said:

One of my favorite phrases in mirroring, "split brain".  

Good short look into some thoughts on what really needs to go into thinking about mirroing beyond, right click, start mirroring...

April 18, 2010 1:55 PM

Ranga said:

Interesting scenario in mirroring. Mirroring is still not very reliable, needs more tweaking and FAULT TOLERANCE!!

See my connect item on a different mirroring scenario: When the mirror server goes offline.

April 20, 2010 11:21 PM

Hugo Shebbeare said:

I agree with Master Davis, therefore it is necessary, I believe as a pre-requisite for auto-failover with mirror in asynch mode, to ensure there is a redundant internet connection between all of the quorum. We have achieved and tested that on our Database mirroring setups to ensure that we never get into that split-brain situation.

Thanks Tibor, nice post.

November 5, 2010 3:23 PM

chaitanya said:

How to make Data access to the users? When both servers are down in MIRRORING



1)what if Server A and Server B are completely down,2)what if Server B and Server C are completely down,3)what if Server A and Server C are completely down

In all the cases we cannot Re-Initialize the Servers which are down

How to make Data access to the users?

plase give me the answer in both synchronous and Asynchronous modes

December 14, 2012 6:32 AM

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