Click here to monitor SSC
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 


Where to locate the Witness server when using Mirroring for DR


Where to locate the Witness server when using Mirroring for DR

Author
Message
mcdba@russweb.co.uk
mcdba@russweb.co.uk
SSC Rookie
SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)

Group: General Forum Members
Points: 28 Visits: 224
Hi,

I am looking into setting up mirroring for DR purposes. What I want to know is the correct location for the Witness server at our DR site? The primary server will be in our office and the target server will be at our DR site.

Thanks in advance.

Russell



Perry Whittle
Perry Whittle
SSCrazy Eights
SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)

Group: General Forum Members
Points: 8866 Visits: 16602
Ideally the witness should be on a third site, if not then place it at the primary site. If you put it at the DR site and you have a network interruption you could end up with unwanted failovers or the principal suddenly going offline.

-----------------------------------------------------------------------------------------------------------

"Ya can't make an omelette without breaking just a few eggs" ;-)
mcdba@russweb.co.uk
mcdba@russweb.co.uk
SSC Rookie
SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)

Group: General Forum Members
Points: 28 Visits: 224
Thanks for the info Perry.

So in the event of a power outage at the primary site where the secondary server will lose communication with both the primay and witness server will it automatically failover?



e4d4
e4d4
SSC Veteran
SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)

Group: General Forum Members
Points: 275 Visits: 2399
Russell101 (5/12/2013)
Thanks for the info Perry.

So in the event of a power outage at the primary site where the secondary server will lose communication with both the primay and witness server will it automatically failover?


No. "If the mirror server is disconnected from the witness and also from the principal server, automatic failover is not possible, regardless of the state of the principal server." http://msdn.microsoft.com/en-us/library/ms175191%28v=sql.105%29.aspx
You should make a good DR plan for different type of outage, and now eg. when perform a manual failover in case of failure.
mcdba@russweb.co.uk
mcdba@russweb.co.uk
SSC Rookie
SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)

Group: General Forum Members
Points: 28 Visits: 224
The systems that I am looking to mirror currently are the management database for our Blackberry Enterprise Server and the configuration database for Active Directory Federation Services. In the event of power loss at the primary site I would like the databases to automatically failover to the DR site. As from what I can tell to manually failover the severs involved need to be able to connect to each other and in the event of a powerloss at the primary site I would then not be able to fail them over.

So given the above do need to place the witness at the DR site after all?



e4d4
e4d4
SSC Veteran
SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)SSC Veteran (275 reputation)

Group: General Forum Members
Points: 275 Visits: 2399
Russell101 (5/12/2013)
...
So given the above do need to place the witness at the DR site after all?


But then if DR site goes down: "Loss of the mirror and the witness

Assume you have configured database mirroring with a witness. When the mirror is unavailable, the principal runs exposed. While the mirror is unavailable, if the witness is also lost, the principal becomes isolated and can’t service the clients. Even though the principal database is running, it is not available to the clients. If you attempt to connect to the database, you get the message “Database <dbname> is enabled for database mirroring, but neither the partner nor witness server instances are available: the database cannot be opened.”

http://technet.microsoft.com/en-us/library/cc917681.aspx#EIAA

So without a third site it depends, I think you should place the witness at the more reliable site.
Perry Whittle
Perry Whittle
SSCrazy Eights
SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)

Group: General Forum Members
Points: 8866 Visits: 16602
Russell101 (5/12/2013)
So given the above do need to place the witness at the DR site after all?

No, for the reasons that have been specified.

-----------------------------------------------------------------------------------------------------------

"Ya can't make an omelette without breaking just a few eggs" ;-)
mcdba@russweb.co.uk
mcdba@russweb.co.uk
SSC Rookie
SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)SSC Rookie (28 reputation)

Group: General Forum Members
Points: 28 Visits: 224
So if I have the primary and witness servers at our main location and we suffer a power outage will the secondary server automatically takeover?



Perry Whittle
Perry Whittle
SSCrazy Eights
SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)SSCrazy Eights (8.9K reputation)

Group: General Forum Members
Points: 8866 Visits: 16602
Russell101 (5/12/2013)
So if I have the primary and witness servers at our main location and we suffer a power outage will the secondary server automatically takeover?


No, more detail on failover scenarios is provided here

-----------------------------------------------------------------------------------------------------------

"Ya can't make an omelette without breaking just a few eggs" ;-)
Go


Permissions

You can't post new topics.
You can't post topic replies.
You can't post new polls.
You can't post replies to polls.
You can't edit your own topics.
You can't delete your own topics.
You can't edit other topics.
You can't delete other topics.
You can't edit your own posts.
You can't edit other posts.
You can't delete your own posts.
You can't delete other posts.
You can't post events.
You can't edit your own events.
You can't edit other events.
You can't delete your own events.
You can't delete other events.
You can't send private messages.
You can't send emails.
You can read topics.
You can't vote in polls.
You can't upload attachments.
You can download attachments.
You can't post HTML code.
You can't edit HTML code.
You can't post IFCode.
You can't post JavaScript.
You can post emoticons.
You can't post or upload images.

Select a forum

































































































































































SQLServerCentral


Search