How to uninstall a SQL server named Instance on a two node SQL cluster

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How to uninstall a SQL server named Instance on a two node SQL cluster

APA0876

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November 26, 2012 at 2:54 pm

#266612

Hi,
I currently have a two node SQL Cluster with two named instances:
SQLinstance1 and SQLInstance2, I want to uninstall SQLInstance1 and install a default instance with a new IP.
How should I proceed.
Thanks!!!

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dan-572483 SSCoach Points: 15870 More actions · Answer 1

To remove clustered SQL instance, you can launch the SQL installation Wizard, Select Maintance and then "Remove node from a SQL Server failover cluster." Start on the passive node, then repeate on the active node.

Frankly though, uninstalling SQL Server completely enough to do a reinstall is fairly tricky, and I would not attempt it in your situation for fear of damaging Instance 2. Instead I would

1) Drop the user databases in the instance you're not going to use anymore.

2) Disable Instance 1 SQL Server Service in SQL Server Configuration Manager. Repeat on both nodes.

3) Delete the Cluster Service for Instance 1 in Failover Cluster Manager. You can then reassign SAN disks if needed for the new instance.

3) Install new instance of SQL Server

I assume the new instance will run on one server only and not be clustered - I'm not sure that "default instance" means anything in a failover cluster, as the Network Name & IP can transfer between one server and the other. (correct me if I am mistaken anyone)

If a new or different IP is all you really need, that can by changed in Cluster Manager. It looks like you can change the DNS name (used by clients to connect to SQL) there as well. I haven't tried that myself, but it seems a heck of a lot easier & less risky than doing an unstall/reinstall of SQL server where there's another instance you don't want to disturb.

APA0876 Hall of Fame Points: 3853 More actions · Answer 2

dan-572483 (11/26/2012)
To remove clustered SQL instance, you can launch the SQL installation Wizard, Select Maintance and then "Remove node from a SQL Server failover cluster." Start on the passive node, then repeate on the active node.
Frankly though, uninstalling SQL Server completely enough to do a reinstall is fairly tricky, and I would not attempt it in your situation for fear of damaging Instance 2. Instead I would
1) Drop the user databases in the instance you're not going to use anymore.
2) Disable Instance 1 SQL Server Service in SQL Server Configuration Manager. Repeat on both nodes.
3) Delete the Cluster Service for Instance 1 in Failover Cluster Manager. You can then reassign SAN disks if needed for the new instance.
3) Install new instance of SQL Server
I assume the new instance will run on one server only and not be clustered - I'm not sure that "default instance" means anything in a failover cluster, as the Network Name & IP can transfer between one server and the other. (correct me if I am mistaken anyone)
If a new or different IP is all you really need, that can by changed in Cluster Manager. It looks like you can change the DNS name (used by clients to connect to SQL) there as well. I haven't tried that myself, but it seems a heck of a lot easier & less risky than doing an unstall/reinstall of SQL server where there's another instance you don't want to disturb.

Hi Thanks, very helpful. This new default instance will be part of the SQL failover cluster. It is a default instance with a new name and IP. As you know a named instance has this format on the name [SQLInstance\Instance] and the default instance it is just [SQLinstance].

This is an active / active sql failover cluster and we need to remove one of the active named instances and substitute one of those named instance by a default instance with a different IP. Have you ever done this using the installation wizard?

Thanks again

dan-572483 SSCoach Points: 15870 More actions · Answer 3

I have not tried this. But I have uninstalled non-clustered SQL Server and was not able to reinstall until I had deleted the C:\Program Files\Microsoft SQL Server folder and the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server registry key, which you wouldn't do if there was another instance on the server you wanted to keep.

You could try deleting just the folder and registry key that refers to MSSQL10_50.INSTANCE1, but unless someone who has successfully done that replies, then you are experimenting, and please respond here what happens.

That's why I suggest just permanently disabling Instance1 (which also allows you to reuse the external storage), and then install a new clustered instance using the Wizard.