June 19, 2014 at 1:00 am
Hi,
One of my client asking mirroring between two server with witness.
Is it possible witness and mirror in same server(with same instance)? OR
Is it possible witness and primary in same server(with same instance) ? if possible can you explain ? OR
Can any one suggest best method to establishing mirroring with in two servers(with witness) ?
June 19, 2014 at 4:00 am
What is the use of witness server if you are placing it on the principal when a fail over occurs both of them go offline
June 19, 2014 at 4:11 am
It's possible, it's not recommended. The witness is there to cast the deciding vote as to whether the principal is down or not, it's not going to be of much use on one of the servers.
Witness doesn't need to be a major server, it doesn't put load on a server. It can be a tiny VM with SQL Express installed on it
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
June 19, 2014 at 4:39 am
SQLBIDeveloper (6/19/2014)
What is the use of witness server if you are placing it on the principal when a fail over occurs both of them go offline
yes, you are correct, If i place witness in principal .
If possible; i will place witness in mirror server so automatically mirror become principal. In this case it very useful, without manual interaction !.
June 19, 2014 at 5:12 am
PRR.DB (6/19/2014)
If possible; i will place witness in mirror server so automatically mirror become principal. In this case it very useful, without manual interaction !.
No, because it can cause false failovers if there's a network drop between the principal server and the one running mirror + witness. Also, once it has failed over, now you have the witness running on the principal, so scenario 1.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
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