I currently host several servers which each have SQL Server and about 150 databases each. The databases all get moderate usage and I'm concerned about IO. Currently I use SQL failover with a witness instance. Each SQL server currently uses 2 x 2TB disks (Western Digital RE4's). My ram is maxed out at 96GB and I believe the disks are my bottleneck. Would using 8 disks to achieve 2TB+ result in much better performance? What do I need for the best IO?