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Database mirroring High Safety (synchronous) with Autofailover - witness availability.. Expand / Collapse
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Posted Monday, September 23, 2013 1:47 AM
Grasshopper

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Hi,

Hope i can get some feedback regarding a scenario we have in an environment that has been designed to use SQL mirroring with autofailover (ie witness) as i have some concerns about running from Datacenter 2 and it becoming unavaialble and hope i can get people's views on how this would work..

Primary instance is usually in Datacenter 1
Secondary instance is usually in Datacenter 2
Witness is always in Datacenter 2

a planned test is done to run production out of out of the secondary instance in Datacenter 2, but whilst running out of there both the witness and secondary (where the database mirror principles are at this time) go down - so as the quorum is lost as such am I able to force service over to the original primary without the the witness being online?

Is there also a way to remove the witness from the mirroring set up via the mirror site (where databases in restoring \ mirror state at this time) so we could run the FORCE_SERVICE_ALLOW_DATA_LOSS command as is possible without a witness being there and bring the databases online in the event of a disaster?

thanks in advance for any responses to this
Post #1497285
Posted Tuesday, September 24, 2013 3:02 AM
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Hi,

here you can find information about mirroring with a witness-server:

http://technet.microsoft.com/en-us/library/ms189902.aspx

you have to put the witness-server in a datacenter 3, to avoid a crash with your mirror, if the datacenter 2 gets offline.
Post #1497715
Posted Tuesday, September 24, 2013 6:15 AM
Grasshopper

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thanks Andreas,

really appreciate your response

yes this is the same article i have researched and as we have 2 DC's when running off the secondary (where witness resides) is when the quorum is lost and they are pretty exposed in regards to failback if that DC goes down..

ultimately monitoring will be done to ensure the instance is running from the primary as much as possible, otherwise they are in the situation where the mirrors need to be broken so that those db's that were mirrors can br brought online..
Post #1497794
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