“ Redundancy refers to the use of multiple servers in a load-balanced environment for any of several purposes, such as to improve farm performance, to scale out to accommodate additional users, and to improve availability.”
“ Availability is a more specialized concept that refers to a multiple-server environment that is designed to accept connections and operate normally even when one or more of the servers in the farm are not operational.”
The dreaded “Cannot connect to the database server…or configuration database…”
SQL Clustering – availability at the SQL instance
SQL Mirroring – availability at the database.
* Mirroring available with SQL 2005 SP 1
Database Mirroring Best Practices and Performance Considerations. Microsoft(r) TechNet. [Online] March 10, 2006. [Cited: 10 09, 2008.] http://www.microsoft.com/technet/prodtechnol/sql/2005/technologies/dbm_best_pract.mspx.
Case Study of High Availability for SharePoint using Database Mirroring (white paper). Microsoft TechNet. [Online] April 2008. [Cited: September 22, 2008.] http://technet.microsoft.com/en-us/library/cc531332.aspx.
Microsoft. How to transfer the logins and the passwords between instances of SQL Server 2005. Microsoft Help and Support. [Online] July 11, 2006. [Cited: October 13, 2008.] http://support.microsoft.com/kb/918992/.
Microsoft. Using Database Mirroring with Office SharePoint Server and Windows SharePoint Services. Microsoft TechNet. [Online] July 24, 2008. [Cited: October 13, 298.] http://technet.microsoft.com/en-us/library/cc262910.aspx.
Talmage, Ron. Database Mirroring in SQL Server 2005. Microsoft TechNet. [Online] April 1, 2005. [Cited: October 14, 2008.] http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirror.mspx.
Microsoft. Setting Up Login Accounts for Database Mirroring. MSDN: SQL Server Developer Center. [Online] September 2007. [Cited: October 14, 2008.] http://msdn.microsoft.com/en-us/library/ms366346(SQL.90).aspx.
Curry, Ben and English, Bill. Microsoft Office SharePoint Server 2007 Best Practices. Redmond: Microsoft Press, 2008.
Plan for redundancy (Office SharePoint Server). Microsoft TechNet. [Online] July 15, 2008. [Cited: September 22, 2008.] http://technet.microsoft.com/en-us/library/cc263044.aspx.
Plan for availability (Office SharePoint Server). Microsoft TechNet. [Online] September 5, 2008. [Cited: September 22, 2008.] http://technet.microsoft.com/en-us/library/cc748824.aspx.