Suppose the following configuration: Drive D ... Data, Drive E .... TempDB, Drive F ... Log. and suppose all drives are on separate spindles with respective drive controllers.
Concerning performance; is the above configuration optimal, decent, or not advisable?
With budgetary constraints in mind, can any of these DB's share the save drive without significant performance degradation?
Which of these drives needs to be the fastest?
This is difficult to answer without a full analysis of your system. For example, to do this properly, we should have an idea what kind of IOPS your system will generate, in order to plan for slightly more capacity than peak load.
I always love RAID10 across the board, separate arrays for everything, and in many instances splitting into different file groups as performance needs dictate.
However, in a budget-constrained environment, here is a decent, basic configuration, for someone who wants to approximate the ideal:
4 separate arrays:
This setup provides decent performance, and higher recoverability chances. For example, in this instance, if your Data array fails, you can still run the server and BACKUP LOG to do a point in time recovery on the failed databases, since you could still access system databases and your transaction logs in the face of data array failure.