Upgrading 32-bit SQL Server cluster to 64-bit

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Here is my situation. $WORK has a trio of three clustered database servers (64-bit Server 2003) that are currently running two SQL Server instances. Unfortunately, when the cluster was set up a couple years ago my organization did not have 64-bit SQL Server licenses, so we installed the 32-bit version of SQL Server 2005 Enterprise for both instances. They have been running fine, and we’re not encountering any limitations of 32-bit SQL Server, so I had not intended to move to 64-bit SQL Server until the hardware (servers as well as SAN) is replaced in about another year. Until I was told that our CMS managers want to move to SharePoint 2010, which requires 64-bit SQL Server 2008; now I need to upgrade much sooner.

I have a plan:

1. The first instance is a default instance hosting about a dozen miscellaneous application databases. I do not intend to modify this instance at all. In other words, the default instance will remain online throughout the upgrade, and will remain on 32-bit SQL Server 2005, with only a couple of short disruptions due to failovers caused by work on the other instance.

2. The second instance is a named instance exclusively for our SharePoint installation. I intend to move this to 64-bit SQL Server 2008 R2 Enterprise. Since in-place upgrading is not available when moving from 32-bit to 64-bit SQL Server, I believe I will need to completely uninstall the current named instance from the cluster (taking full backups first, of course), then reinstall a new 64-bit SQL Server 2008 instance with the same name as the previous instance. I will then restore the old databases from backup.

And I have some questions:

1. Is the above plan reasonable? Any glaring misconceptions on my part? Is there an easier way to do this?

2. There is no available space on the SAN, so I cannot set up a third instance and migrate the databases over to it (my preferred method). As far as I can tell, a complete reinstall is necessary in this case. Correct?

3. Will there be any issues running one 32-bit SQL Server 2005 instance on the same cluster alongside a 64-bit SQL Server 2008 instance?

4. Will installing a new named instance with the same name as the previous named instance cause any trouble?

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1. Yes. Don’t forget to script out the logins using sp_help_revlogin (you’ll need to Google for it and put the stored proc on your system) so that you can just restore the databases without having to recreate the logins. You’ll also need the jobs, etc. You can just restore the system databases if you are installing the 64bit version and you are installing the exact same build.

2. Yes a full reinstall is needed.

3. No.

4. No.

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