As I understand it Windows Server 2008 R2 has the ability to send IO requests to the storage subsystem of up to 1MB in size. Back in the Server 2003 era (and before) this used to be limited to 64KB.
I seem to remember reading that it was possible to manipulate the maximum IO request size away from the default value. I think that a registry key under HKLM\SYSTEM\CurrentControlSet\Control\Session Manager is required but Google isn't finding any answers today.
I want to change the IO requests size to asses the impact on a VMWare FT virtual machine when it is hosting a specialist video recording application that is doing a lot of IO to virtual disks. The root problem we are trying to address is one of VMWare FT Primary/Secondary replication convergence when experiencing a mix of large read and write requests. The hope is that by varying the IO request size we may be able to increase the efficiency of this.