February 7, 2012 at 7:15 am
Hi all
With reagards to the AlwaysOn high availibility features for database mirroring in SQL 2012
Are these features only available for Clustered instances of SQL Server?
Thanks
February 7, 2012 at 7:35 am
First things first...
It's not Always On Database Mirroring. Database Mirroring and Always On are two different things. The older style database mirroring (as in 2005 and 2008) will still be there as-is, unchanged.
AlwaysOn requires windows clustering to be installed, but unless I'm completely mistaken, the instances don't have to be clustered, they just need the clustering service bits installed
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
February 7, 2012 at 7:41 am
The older style database mirroring (as in 2005 and 2008) will still be there as-is, unchanged.
I thought that a change is 2012 was that the mirror(secondary) database would allow for read only transactions in 2012
AlwaysOn requires windows clustering to be installed, but unless I'm completely mistaken, the instances don't have to be clustered, they just need the clustering service bits installed
When I tried to activate AlwaysOn on SQL Config Manager, it says:
this computer is not a node in a cluster
February 7, 2012 at 7:57 am
derekr 43208 (2/7/2012)
The older style database mirroring (as in 2005 and 2008) will still be there as-is, unchanged.
I thought that a change is 2012 was that the mirror(secondary) database would allow for read only transactions in 2012
That's AlwaysOn. Database Mirroring is still there, the same as it was in 2008. Two different features.
AlwaysOn = new in 2012, readable secondaries, multiple secondaries, etc.
Database Mirroring = same as 2008, mirror is unavailable (unless using snapshots)
AlwaysOn requires windows clustering to be installed, but unless I'm completely mistaken, the instances don't have to be clustered, they just need the clustering service bits installed
When I tried to activate AlwaysOn on SQL Config Manager, it says:
this computer is not a node in a cluster
Sorry, it appears they do have to be part of the same windows cluster group. It's SQL that doesn't have to be clustered.
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
February 25, 2012 at 5:32 am
Yes,
It's not necessary to have the SQL clustered Instance. You need the window cluster only for AlwaysOn Availability Groups.
March 2, 2012 at 11:25 am
Sorry for the spray of questions.
Would this allow statistics to be generated on the secondary?
Can the secondary have indexes that the primary does not have?
During a disaster of the secondary site, can a restore be done on the secondary independant of the primary, or will the secondary site need to wait for a full snapshot from the primary site to be generated?
March 2, 2012 at 11:52 am
benjamin.reyes (3/2/2012)
Would this allow statistics to be generated on the secondary?
Yes, temporary stats in TempDB. Search for AlwaysOn Statistics
Can the secondary have indexes that the primary does not have?
No. It's read-only
During a disaster of the secondary site, can a restore be done on the secondary independant of the primary, or will the secondary site need to wait for a full snapshot from the primary site to be generated?
Snapshot?
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
March 2, 2012 at 12:02 pm
GilaMonster (3/2/2012)
During a disaster of the secondary site, can a restore be done on the secondary independant of the primary, or will the secondary site need to wait for a full snapshot from the primary site to be generated?
Snapshot?
Sorry improper term. Is it possible for the secondary to recover from a local backup, or does it need to wait for the primary to generate another secondary, if something happens to the secondary or the server it is on.
March 2, 2012 at 1:19 pm
How do you recover a failed database mirroring secondary? AlwaysOn will be (mostly) the same.
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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