Solve SharePoint Performance Problems in SQL Server

Most poorly performing SharePoint sites are caused by underlying SQL server configuration, or lack there off, settings.
One of the big impacts of using SharePoint Central Admin to create content databases is that they will be based on the Model DB template.
This results in the following:
Data File = 10Mb with auto grow = 1Mb
Log File = 1Mg with auto grow = 10%
This means that almost every time a user saves an office document, SQL will have to "auto grow" the database files and there is an overhead to this operation. The SQL Disk Usage report will give you an indication of this impact on existing content databases that started with the default size.

This is a relatively small content database but has already been extended many hundreds of times with 45ms per second in this case.
Extending the Database (data and log files) manually to a size that would provide for 6/12 months projected storage requirements results in a noticeable improvement in end user response times not only for saving documents but in overall responsiveness of all sites in the database.
There is much more to designing a good SQL platform for SharePoint, this is just some evidence in case you didn't believe it...