If you are planning to use NetApp as the SAN for your SQL Server instance(s), take a look at these documents in addition to the normal SQL Server IO planning best practices documents.
TR-3779 Sizing best practice guide. http://media.netapp.com/documents/tr-3779.pdf TR-3696 This is for the storage layout best practices.http://www.netapp.com/us/library/technical-reports/tr-3696.html White Paper on 1 TB DSS systemshttp://www.netapp.com/us/library/technical-reports/tr-3650.html SMSQL 5.0 Best Practice Guidehttp://media.netapp.com/documents/tr-3431.pdf Microsoft® SQL Server 2005 Performance and Scalability Testing Using NetApp FAS920 Storage Systemshttp://media.netapp.com/documents/tr-3402.pdf