SQL Server Tips by Robin Schumacher

Data/Code Positioning

Data, code, and object definitions that reside in memory have a much higher return rate than objects that must first be retrieved from disk and placed into memory. The latest numbers on this topic suggest that data can be accessed from RAM around 1,400 times faster than on physical disk.

While database engines differ in the layout of the memory structures used to hold data and other necessary items, they all contain areas that function to speed the delivery of data and to lookup information. The percentage of times the database can serve information from memory instead of disk will contribute mightily toward overall database speed. Things such as data being available in the SQL Server cache and stored procedure definitions being nestled into memory all play a part.

Of course, hardware design counts, too. Fast drives and load segmentation both play a part. Contention at this level; however, normally falls under resource availability.

The above book excerpt is from:

High-Performance SQL Server DBA
Tuning & Optimization Secrets

ISBN: 0-9761573-6-5
Robin Schumacher

 http://www.rampant-books.com/book_2005_2_sql_server_dba.htm