October 25, 2007 at 11:10 am
We've successfully prototyped SQL 2005 Database Mirroring for 2 very small DB's in our development environment. My mgm't wants to know more about the product. Feedback to any of these questions is much appreciated:
Questions regarding SQL 2005 Database Mirroring
1. How are you notified if Mirroring fails?
2. Using "High Protection Mirroring" (no Witness because we want to control the failover) what happens if the apply to the Mirror fails? (does the Principal wait until the failure is resolved?)
3. How do you monitor the Mirror process? (the DoubleTake product offers a dashboard-like presentation)
4. Does Mirroring accomodate transactional replication - in other words, are all the rules (including horizontal row filters) propagated to the Mirror?
5. Can anyone share knowledge comparing DoubleTakes performance to SQL 2005 Mirroring performance?
October 25, 2007 at 9:59 pm
I don't know about DoubleTake, but I can answer some of your other questions:
1 & 3) From SSMS you can access the Mirroring Monitor by right clicking one of the databases and selecting from the menu. You need to register the mirrored database, and then you can see the current status of the link between the databases. There is a tab that allows you to set the criteria for notifications (eg latency). I think the status auto-refreshes once a minute while the monitor is open, or you can refresh manually - if it has been less than 15 seconds since the last refresh then the command is ignored.
If I remember correctly, a job is created when you set up mirroring that will monitor the status for you, but you need to add the schedule manually. This job will create logged errors (I think 32040 ...) that you can set up alerts against. Also you can track the WMI notifications that are generated when the state of a connection changes.
It's worth going through the BOL entries for mirroring which have this info in more detail; they also give detailed scripts to set up the alert jobs.
2) If the mirror server becomes unavailable for any reason, the primary essentially acts as an unmirrored database. When the mirror becomes available again, the outstanding log records are moved over (synchronizing state) until the two databases are in sync again (synchronized state).
4) Mirroring synchronizes everything in the database. Anything outside of the database (jobs, msdb info, distribution database, logins etc) will not be mirrored.
Matt.
October 29, 2007 at 7:49 am
Thanks so much for your reply. FYI, I found a pretty decent Microsoft transcipt on MIRRORING questions & answers:
http://www.microsoft.com/technet/community/chats/trans/sql/sql_102704.mspx ? many questions/answers here
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