DAS or SAN for SQL Server?

Performance issues is always complicated, but a common approach is possible (in fact the only way to work through this is to define the problem area and structure the different factors into groups). In my approach the operation platform is one key group while the database is another. Based on the work I have done since September, I have found it very hard to get real and trustworthy information about the utilization of SAN storage when this is used for SQL Server. And as a advisor I don't have deep knowledge about the solutions from the indivdual SAN vendors (expertice and experience required). In my mind the old rules about separation of physical I/O from the I/O characteristics still applies despite the fact that SAN's normally have high end controllers capable of handling huge I/O loads. DAS (Direct Attached Storage) as the traditional way of providing storage, seems to be much easier to work with when analysing performance issues at the database level mainly because good old Performance Monitor will tell you all you have to know to conclude and defined possible counter measures. This is NOT the same for SAN's! Since a SAN mainly is used for storage provision and consolidation, you have to work your way through the hole SAN setup and identify every piece of software that is generatig I/O against the SAN. Add some interconnect (normally fiber switches, HBA's etc.) in between and you have multiplied the complexity by at least PI.

Add another overhead for hosted solutions where several customers normally share the same infrastructure and the picture starts to be rather though to control. During my search I found another blog discussing the same issues and his summary resembles much of my own experience.

So this is yet another example of how developments in technology actually complicates the everyday work for both customers and consultants, and this is clearly something to account for when doing the TCO matrix.

Based on this, customers should evaluate SQL Server storage and consider to implemented database storage as DAS. Do you agree?