Aliasing the SQL Server name

Question

I'm creating a new SP 2010 farm that will replace our existing 2007 farm (using the db attach method), and decided I should probably use SQL aliasing with this install. So 2 questions relating to this.

1) There's 2 ways I can alias my SQL Server name: Create a local SQL Alias using cliconfg, or create a new DNS Host (A) record that also points to my SQL Server. My understanding says that either one should work, provided that SQL Server is using the default instance. However, if the instance name changes, then using a DNS based alias would still require me to update my database server names in SharePoint. However, a DNS alias would mean I'd only have to make a single DNS change, rather than changing the SQL alias with cliconfg on each SP server. Is that all correct?

2) For either of the SQL Alias or DNS Host (A) records, how does that affect SPN creation for Kerberos authentication and delegation? For SQL Aliases, should my SPNs point to the actual server\instance name, and for a DNS record, point to the DNSAlias\instance?

Thanks, Evan

Answer 1

1) That's all correct. I would go for a SQL alias because it provides resiliency against port and instance name changes on your SQL server. It also allows you to specify more than 1 alias, you could for example create an alias for each content database for flexibility. The downside (maintaining them on all your servers) remains however.

2) This does not affect your Kerberos SPN records, because the SQL client tools convert your requests to the proper SQL instance. So just create your SPN's as if the SQL alias would not be there.